5627
RESPONSE TO PUBLIC COMMENT - DISSOLVED OXYGEN CRITERIA
After review of all the comments received during the public
comment period following the announcement of their Availability
in the Federal Register the agency has prepared vhe following
response. A total of 25 respondants submitted comments, and
except for a few redundant points, each comment has been answered
individually.
Comment; Since the dissolved oxygen levels found in most lakes
and streams appear to be satisfactory now under the current
dissolved oxygen standards that the states have adopted pursuant
to the 197.6 EPA criteria, we question the need to propose
criteria that would represent a major departure from previous
criteria.
Response; EPA has a number of reasons for updating the water
quality criteria for dissolved oxygen:
1) EPA is required by law to publish water quality criteria
that reflect the latest information on the water quality
requirements of aquatic organisms. A 10-year period has passed
since the last dissolved oxygen criteria were issued. During
this 10-year period most of the important toxic chemical criteria
have been reviewed and reissued once, and several twice. Because
of the importance of dissolved oxygen a review was started in
1981 and the currently .proposed criteria are the result of that
review.
2) EPA has been systematically revising single-number
criteria in favor of two-number criteria: 1) to minimize the cost
of overly stringent criteria that can be exceeded for short
periods of timev without significant effect; and 2) to provide
criteria that provide a meaningful estimate of the acutely lethal
threshold. In addition, EPA wishes to avoid underprotection in
situations where the 5 mg/L concentration of dissolved oxygen
cited in the old criterion is not a protective level over longer
periods of exposure.
3) EPA believes that the proper application of the
dissolved oxygen criteria requires a more thorough review and
discussion of the literature than provided in the previous
dissolved oxygen criterion. The requirements for dissolved
oxygen and the effects of low dissolved oxygen concentrations are
much more complex than can be communicated in a single number.
From a regulatory perspective the 1976 dissolved oxygen criterion
represents a reasonable standard in many situations, but it does
not provide sufficient guidance for the user to. judge when it
should be applied or when it could or should be modified.
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4) One of the field examples given in support of the 5 mg/L
criterion in 1976 has since been shown to be in error. Dissolved
oxygen concentrations in Lake Titicaca are now known to be about
7 mg/L rather than the 5 mg/L value cited in the 1976 criterion.
5) The. measurement of dissolved oxygen in the immediate
environment" of developing salmonid embryos and alevins is a
difficult technical task compounded by timing, location, and
method of sampling, by difficulty in estimating the rate of water
flow through the gravel, and by the necessity of determining the
relative contributions of ground-water and surface-water flows.
The agency has provided an alternative approach in the new
criteria, one that may be used in lieu of intergravel sampling
for dissolved oxygen. The agency believes that providing a
choice of methods is preferable to the 5 mg/L intergravel
dissolved oxygen concentration specified in the old criterion, a
value that has been incorporated into only one state's water
quality standards.
6) EPA wished to update the dissolved oxygen criterion with
information and guidance for dealing with waters containing
naturally low dissolved oxygen concentrations.
Comment: The guideline document states that EPA guidelines for
deriving criteria for toxicants (45 FR 79318, November 28, 1980)
are not applicable because the data base types are different. It
would be more appropriate and accurate to state that the
guidelines are not applicable because dissolved oxygen is not a
pollutant, but a naturally varying water quality condition. In
contrast, toxic substances are pollutants.
Response: The pollutant vs. nonpollutant argument is
questionable. Toxic pollutants have a range of toxicities, acute
and chronic raechandsms, target organ specificities, etc. The
physiological effects of any two toxic chemicals selected at
random are almost certainly more different than the similar
responses elicited by low dissolved oxygen and certain pollutants
(eg. cyanide). Also, similar mortality, growth, and fecundity
effects are likely to be similar in their population impacts
regardless of whether the causative agent is a toxic pollutant or
inadequate dissolved oxygen supply.
If the data base for effects of low dissolved oxygen
concentrations contained standard LC50 and chronic test data the
agency would follow the national guidelines as closely as
possible until it became clear that the results were
inapplicable. Obviously certain modifications would be required
in the calculation of acute thresholds from LC50 data and the
averaging periods would probably need to be modified.
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Comment: The statement that some coolwater fish species
mentioned are deemed closer to salmonids in sensitivity than most
warm water species should be specifically referenced.
Response: The agency will both clarify and document its
statements regarding the relative sensitivity to dissolved oxygen
of salmonids/ coolwater fish/ and warmwater fish.
Comment: The assumption EPA makes, that dissolved oxygen
criteria to protect fish, will also protect invertebrates present,
only makes sense if criteria are set at a level to protect the
most sensitive fish in the impacted area. To lump all non-
salmonid fish in one category is rather a simple-minded approach.
Dissolved oxygen requirements vary greatly among this non-
taxonomic grouping.
Response; The agency recognizes the fact that there are many
species of non-salmonid freshwater fish (about 600 species is the
figure we cite on page 10 of the criteria document.) The agency
has provided the option to use cold-water criteria for the more
sensitive non-salmonids, although we anticipated this approach
only for other coldwater or coolwater species. We view the
lumping of all warmwater fish as a necessarily simple approach.
The only reasonable alternative is an arbitrary safety factor to
account for more sensitive species among the many, many species
for which no data exist. Procedures for selecting such a factor
might also be called simple minded, and would most certainly be
called arbitrary.
Comment; On page 2 of the ambient water quality criteria for
dissolved oxygen the report alludes to the fact that some non-
salmonids may require high dissolved oxygen concentrations. I
feel the list is probably incomplete. Organisms adapted to
riffle habitats ;should well be examined for their dissolved
oxygen requirements. These areas are usually high in dissolved
oxygen relative to other stream sections.
Response; The agency agrees that the list is probably
incomplete. This is evident in the subject statement, "...among
the non-salmonids of likely sensitivity are...", which clearly is
not meant as an all-inclusive list. The commentor is correct
that riffle-dwelling species are apt to have relatively high
dissolved oxygen requirements, and addition of a statement
acknowledging this probability will be added.
Comment; We are concerned about dissolved oxygen requirements
for threatened and endangered species. If dissolved oxygen is
allowed to approach 3.5 mg/L for 7 consecutive days, certain
protected riffle-dwelling species may well be impacted. Current
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state law prohibits such action and a permit would be required
for stream sections so affected. Before we would condone such
actions/ studies must be evaluated on the potentially impacted
threatened and endangered species. Low dissolved oxygen
concentrations would also occur when species are already
subjected to stress from high temperatures and other low flow
stresses.
Response; Under the criteria guidance/ the lowest 7-day mean
minimum acceptable would be 4.0 mg/L. Assuming the worst case
(with no diel dissolved oxygen cycles)/ the dissolved oxygen
concentration could be between 3.0 and 4.0 for 3 to 4 days. The
agency is aware of no data that would suggest that any lethality
would result from such an occurrence. The presence of threatened
and endangered species would certainly be a valid consideration
in establishing a higher local standard for the protection of
such species.
Comment; The proposed document does not review the dissolved
oxygen requirements for freshwater aquatic life but rather
reviews the dissolved oxygen requirements needed to support fish,
especially the salmonids. The statement in the criteria document
that "If fish populations are supported/ invertebrate species
would probably be adequately protected" should be documented.
The reference section of this document does not contain any
papers dealing with dissolved oxygen requirements of
invertebrates/ about 10/000 described species.
Response; The agency based its decision to concentrate on the
dissolved oxygen requirement of fish on the paucity of data
available to Davis/ Doudoroff and Shumway, and Alabaster in their
dissolved oxygen criteria reviews/ their conclusions of
invertebrate sensitivity vs. fish sensitivity/ and the impression
that no significant amount of new invertebrate data were
available. The fact that several commentors either wished to see
invertebrates discussed and/or disagreed with the generalization
that protecting fish would probably protect invertebrates/ has
caused us to re-evaluate our position. A new section will be
added to the document for the purpose of reviewing existing data
on the effect of low dissolved oxygen concentrations on
freshwater invertebrates. We are sensitive to the view of some
that the approach adopted in all past criteria (to assume that
protecting fish means protecting invertebrates) is
unsatisfactory. We still hold to our position that "In the
absence of data to the contrary/ EPA will follow the assumption
that a dissolved oxygen criterion protective of fish will be
adequate." However/ we will review the. existing data on the
dissolved oxygen requirements of invertebrates. We are concerned
that laboratory testing of riffle-dwelling species may be
compromised by unnaturally low flow conditions because/ like many
relatively passive ventilators/ their dissolved oxygen
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requirements are flow-dependent. We will be wary of studies that
do not adequately describe flow.
Comment: Maximum metabolic performance in fishes is discussed.
We suggest concentration on survival only/ since natural
conditions are stressful in summer and maximum metabolic
performance is not attainable.
Response: The statement that reduction in dissolved oxygen
eventually causes a reduction in an organisms maximum metabolic
performance is important. This does not imply only that low
dissolved oxygen will prevent an organism from achieving a level
of metabolic performanmce (growth/ feeding/ swimming) that it
might otherwise achieve under optimal conditions/ but also that
it will reduce the metabolic performance under any set of
suboptimal conditions from that otherwise attainable with more
dissolved oxygen present. Thus/ in summer/ some level of
metabolic performance is maximally attainable/ but lowered
dissolved oxygen concentrations can reduce that maximum. In
fact/ it is more likely to limit maximum performance in summer
than at other times of the year.
Comment: The importance of physiological impacts to an
organism's survival/ growth/ and other functions should not be
minimized. Although data are presently lacking/ measurement of
physiological effects may eventually provide an alternative to
evaluating impacts of low dissolved oxygen or other conditions on
organisms. It may be premature to state that "significance [of
physiologic effects]...must be indirect" and that more
extrapolation and assumptions are required to use this type of
data in the development of dissolved oxygen criteria. Rather/
the document should state this type of data is beneficial to
development of water quality criteria/ but is currently very
limited and difficult to analyze.
Response: The agency stands by its stated position. There is a
significant amount of physiological data on dissolved oxygen and
it is not particularly difficult to analyze in a physiological
context. We agree that the physiological data are difficult to
analyze (we prefer "apply") from the standpoint of effect on the
organism/ population/ and community. Physiological data are
indirectly valuable to the criteria establishing process in a
variety of ways and may eventually be shown to have direct
applicability.
Comment; The document indicates that low/ non-fluctuating
dissolved oxygen concentrations experienced by fish over a long
period of time affect growth and harvest rate. An attached
report indicates that fish planted in American Falls Reservoir
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could survive/ grow and contribute to a sport fishery in the
reservoir and below the dam. Data in the report show a growth
rate that is enviable in either a natural setting or a commercial
fish rearing facility. The data from the American Falls project
in Idaho provide a "real world" example which argues convincingly
against the coldwater criteria proposed in the document.
Response; This commentor provided a study of a planted trout
fishery in and below American Falls Reservoir on the Snake River
in Idaho. The study has been added to the criteria document
section on field studies. The commentor suggested that the data
argue convincingly against the proposed coldwater criteria. No
such conclusion could be reached because the dissolved oxygen
concentrations cited in the report indicated that the thriving
put-and-take fishery existed under conditions that: 1) always met
the 3 mg/L instantaneous minimum; 2) always met the 5 mg/L seven
day mean minimum; and 3) met the 6.5 mg/L 30-day mean over 90% of
the time one year and 100% of the time the other two years of the
study. The lowest 30-day average during the approximately one
month period below the 6.5mg/L criterion was about 6 mg/L,
suggesting a brief period of slight production impairment.
It is hard to conceive how the presence of a good fishery under
conditions that met the criteria can be held as an argument
against the criteria.
Comment: The American Falls Reservoir report also indicates that
angler harvest rates of these fish do not correspond to lower
dissolved oxygen concentrations as was cited in the criteria. In
fact/ the rainbow trout catch rate in the 6.7 mile reach below
American Falls Dam was highest during periods of decreased
dissolved oxygen concentration (when readings were more
frequently nearer the 5 mg/L concentration). These catch rates
were 0.66 fish/hr in 1981 and 0.64 fish/hr in 1982, and represent
excellent return-., .to creel rates for a body of water as large as
the Snake River) especially considering the large size and
"quality" of the rainbow trout in this reach.
Response; The report on the American Falls contains findings
counter to those contained in a similar study from Missouri and
cited in the criteria document. Thus, the Missouri study found
that lowered dissolved oxygen concentrations reduced the harvest
rate of rainbow trout/ but the Idaho study found an increased
rate. The decrease was hypothesized to be an effect of decreased
activity, the increase a case of crowding of fish due to
avoidance of unfavorable conditions. EPA believes that both
studies resulted in valid conclusions and that while lowered
dissolved oxygen may decrease fish activity it may also result in
avoidance and concentration of fish in more favorable areas.
The Idaho report has been added to the section on field studies.
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Comment: The criteria document states that given adequate flow/
the weight attained by salmon and trout larvae prior to feeding
is decreased less than 10% by continuous exposure to
concentrations down to 3 mg/L Temphasis added); and that no
effect was found when embryos were incubated at concentrations
above 2 mg/L. Assuming a 3 mg/L difference/ discussed in the
criteria/ is critical to achieve intergravel concentrations/ how
can the EPA justify the conclusion for national criterion that
9.5 mg/L in the water column and 6.5 in the gravel are required
for protection of embryos and larvae?
Response: There are two major factors that are ignored in this
comment. First/ the "adequate flow" discussed in the document is
a 100 cm/hr apparent velocity (flow volume/cross-sectional area)
through the gravel. Flows above this value have relatively
little effect on oxygen supply to the embryos (and larvae)/ but
flows below 100 cm/hr significantly reduce the amount of oxygen
available to the the embryos. Flows measured in field studies of
intergravel conditions are usually much lower than the 100 cm/hr
figure cited in the criteria document. Second/ the effect on
weight attained before feeding starts is only one of several
factors measuring the adequacy of the dissolved oxygen supply to
the embryos. Other factors are size at hatch/ timing of hatch/
and survival. Studies cited in the document contain reports of
smaller size at hatch and delay in hatching when velocities are
below 100 cm/hr and dissolved oxygen concentrations are below
about 6 mg/L. In addition/ the field study of Coble found lower
survival when dissolved oxygen values " were below 6"
velocities were below 20 cm/hr. Since the completion of the new
dissolved oxygen criteria another study has been published that
contains the report of reduced survival of rainbow trout embryos
and larvae whenever the intergravel dissolved oxygen
concentrations fall below 6 mg/L. The agency is still evaluating
the new study.
Comment: Assuming that the 10% reduction in growth rate found by
Brannon/ and Chapman and Shumway (criteria document page 9) / at
concentrations down to 3 mg/L for extended periods of time were
true for the Snake River below American Falls/ and assuming that
dissolved oxygen concentrations fell to 3 mg/L for a 24-hr
period/ what would the actual impact to the overall growth rate
of a fish be? Calculating from growth rate data cited above/
daily growth would be retarded 0.00235 inches. At this rate it
would take 425 consecutive days of depressed oxygen
concentrations for fish growth to be retarded by one inch!
Response ; This comment concerns the 10% growth impairment for
TaFvaT~~salmonids and its application for the growth of catchable-
si ze trout, at a field site. This respondant misapplied the
effect data from larval fish to juvenile and adult fish. In
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fact/ the potential growth effect for older fish is far more than
the 10% reduction cited. A more appropriate figure would be the
33-47% reduction seen with six species of salmonids during the
juvenile (post-larval) stages. It should be noted that the
growth data in the criteria document relate to weight and not to
length.
Comment; The differential of 3 mg/L between intergravel and
water column dissolved oxygen criteria for salmonid spawning has
a very limited data base consisting of two unpublished masters
theses. We believe that the EPA should not include references
that have not been published or peer reviewed. In fact/ this
differential and the acceptable intergravel dissolved oxygen
concentration should be variable depending on several site-
specific factors. We do not believe that a sound scientific
basis exists at present to establish a specific differential/ and
we recommend that the present criterion for salmonid spawning
beds of 5.0 mg/L minimum dissolved oxygen in the intergravel
water be retained.
Even though the document cautions that "if either greater or
lesser differentials are known or expected/ the criteria should
be altered accordingly," we believe that it would be difficult
for the states often lacking complete resources to evaluate the
soundness of the ELS criteria based on the 3 mg/L differential in
given situations. We believe that the EPA has the responsibility
for providing a sound technical basis for any differential- Tt
proposes/ particularly since the result likely would be very
stringent dissolved oxygen requirements in the water column.
Response: The agency would like to take this opportunity to
further explain the reasons for proposing the differential
method. The intergravel dissolved oxygen criterion is found in
only one state's water quality standards. Furthermore, the
agency believes that gathering intergravel dissolved oxygen
values at the proper time and location is difficult and cannot be
expected as a regular monitoring procedure. The proposed new
criteria lists both a water column dissolved oxygen concentration
and an intergravel concentration that the water column is
intended to provide. Those states wishing to utilize direct
intergravel monitoring can certainly do so using the new
intergravel criteria numbers in lieu of the water column values.
Thus/ the new criteria do not preclude use of the Red Book
approach; the agency has merely provided an easier alternative
short of requiring no reduction below natural background
concentrations (an approach currently used by two states).
The agency approach also provides for site-specific
modification of the differential factor/ an approach this
commentor called "too difficult for states lacking resources to
evaluate the appropriateness of the 3 mg/L differential in their
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waters." EPA believes that validating the differential is much
less costly than implementing the same intergravel measurements
in a routine monitoring program for implementing the Red Book
intergravel oxygen criterion.
The differential approach was identified by the agency as a
possible alternative to intergravel criteria per se/ and search
for suitable data was undertaken. The scarcity of such data
highlighted the difficulty in using intergravel dissolved oxygen
measurements and the lack of its use since the issue of the 1976
Red Book. Two masters theses were found and judged to be of
acceptable quality by EPA. These thesis studies were conducted
by students under the direction and review of graduate committees
including noted scientists in the field of dissolved oxygen
requirements of fish. In addition/ theses provide much more in-
depth presentation of methods and data, providing the reader with
a great deal of information to use in evaluating the quality of
the research. These data were judged to be valid and reasonably
consistant between the two studies.
Comment; The 3 mg/L differential was developed from data
collected only from two small/ forested streams which exhibit
substantially less than adequate water flows/ streams atypical of
those likely to be affected by the proposed criteria. Data from
larger rivers more likely to be subjected to development/ would
be more appropriate to examine. Since larger rivers would very
likely exhibit higher water velocities through the intergravel
spaces/ the conclusions based solely on the two studies cited are
completely inadequate to base the proposed criteria.
Response; Intergravel water flow is primarily determined by pore
size/particle size and hydraulic head. Selection of the former
is likely to be -..fish-species and fish-size dependent/ and there
is no simple relationship between stream size and the size of
spawning fish. Large gravel and pores can have smaller
velocities of water flow that small gravel and pores at a given
hydraulic head. Finally/ hydraulic head is often a function of
stream gradient and gradient is usually greater in small streams
than in large streams.
Comment; Because there is relatively little data on non-salmonid
fish, EPA has been very cautious in establishing criteria for
their protection. This is especially so for the 5.0 mg/L
criterion for early life stages. EPA1 s interpretation appears to
be overly conservative for the following reasons: 1) the more
sensitive non-salmonids were those spawning in the earlier spring
months/ while summer spawners such as the sunfish were less
sensitive; and 2) EPA has interpreted the means of dissolved
oxygen concentrations in these studies as if they were the minima
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observed during the studies/ when in fact the minima were often
0.5-1.0 mg/L lower.
He believe that the data properly analyzed for means and
minima would support only a daily average of 5.0 mg/L with a
minimum of 4.0 mg/L. Concentrations of dissolved oxygen that may
be needed to protect spring spawners probably should not be
extended to summer months when less-sensitive non-salmonids are
spawning.
Response; The point raised by the respondant regarding the
agency's interpretation of the means from the early life stage
tests is a valid one. Bach of the studies cited will be
reanalyzed to determine the variability in the exposure reported
by the investigator. The channel catfish data have been reviewed
with the author of the paper with respect to when the mortality
occurred and what the range and -mean of the dissolved oxygen
concentrations were during pre- and post-hatch phases of the
study. The author also identified several typographical or
author, errors in the published tables. EPA1s analysis of this
study is that very little variation occurred in exposure
concentrations, and that criteria established on means or minima
would only vary by about 0.3 mg/L.
The question of the sensitivity to low dissolved oxygen
concentrations of spring vs. summer spawning, non-salmonids is
another perceptive observation. There is no question that the
more sensitive non-salmonid early life stages belong, in general,
to earlier spawning coolwater species/ and that most of the more
typical warmwater fish appear to have less-sensitive early life
stages. However, of the four more-sensitive species, one, the
channel catfish is a typical warmwater species/ and review of the
channel catfish data with respect to means and minima did not
alter the agency's estimation of the safe concentration for this
species. .'./•
It is apparent to both the agency and the commentor alike that
the amount of information on the dissolved oxygen requirements
of warmwater fish leaves much to be desired. EPA would like to
point out that the proposed minimum dissolved oxygen criterion
for warmwater fish (pooling all life stages) is 5 mg/L/ the same
value cited in the 1976 Red Book. Any increased stringency in
the new criteria comes about as the result of the 7-day mean
value of 6.0 mg/L. Depending on the magnitude of diel cycles,
this may or may not be effectively more stringent (more on this
point later).
Comment; No data on reproduction or behavior of channel catfish
is reported.
Response; No data on the effects of dissolved oxygen on channel
catfish reproduction or behavior were found. The comment
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contained no reference to any such data that was overlooked by
the agency/ so we assume the comment refers to the absence of any
such data rather than its being missed by the agency.
Comment: The statement that "In most cases/ no mortality results
from acute exposures to 3 mg/L for the duration of the acute
tests" should include ranges of the acute test. As is/ the
reader has no idea of the duration of the tests.
Response; The agency agrees that a statement regarding duration
of exposure would be better and one will be added.
Comment: The species of non-salmonid fishes (early life stages)
should be listed along with the documentation of the
concentrations of dissolved oxygen that caused stress to these
species.
Response; Figure 1 in the criteria document contains a summary
of the available data on the relationship between dissolved
oxygen and survival of early life stages of non-salmonid fish.
For the more sensitive species it is apparent that little or no
survival occurs at 3 mg/L and 50% mortality occurs at 4-5 mg/L.
The agency believes that this visual summary is preferable to a
table that would include the variety of data presented in this
figure and in the section on early life stages of non-salmonids.
Comment; Reported data on channel catfish survival on p. 12
appears to be contradictory and the opposite of what might
reasonably be expected. As stated/ embryonic and larval stages
are more tolerant to lower dissolved oxygen concentrations at 28
C than they are at 25 C. If correctly cited/ the reason for this
response should be' explained.
Response; Although the citation appears contradictory to the
agency's general observation of the greater effect of low
dissolved oxygen at higher temperatures/ the contradiction is not
particularly significant because the temperatures are so similar.
The growth reductions seen at 25 C and 4.0-4.4 mg/L were 31% and
56% (avg. 43.5%); the comparable values at 28 C and 3.7-3.9 mg/L
were 9% and 33% (avg. 21%). EPA believes that this relatively
small inversion is not a true temperature effect/ but merely
reflects experimental variability (differences in duplicates at
the same temperature were 25 and 24%/ respectively).
Comment; The avoidance of areas of low dissolved oxygen
exhibited by certain fish is discussed in the criteria document.
The document states/ "The environmental significance of such a
response is unknown/ but if large areas are deficient in
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dissolved oxygen this avoidance would probably not greatly
enhance survival." On many streams, naturally-occurring aquatic
macrophytes may cause relatively small localized pockets of low
dissolved oxygen during periods of low photosynthetic activity.
The ability of fish to avoid such areas should be an important
consideration in applying dissolved oxygen criteria. We believe
that the following sentences should be inserted immediately
following the above quoted sentence in order to more completely
discuss the avoidance response:
"If areas of low dissolved oxygen are limited to a
relatively small portion of a water body, then the fishery may
successfully avoid these areas. In these cases, the fishery may
be influenced to a much greater extent by the higher dissolved
oxygen that dominates the water body."
Response: Criteria define conditions for the well-being of
aquatic organisms. Avoidance usually indicates conditions not
consistant with the well-being of the organisms. Therefore,
avoidance has no role in establishing criteria, but in applying
criteria such site-specific factors may be appropriate.
Consider, however, that if space or food resources are limiting,
avoidance could affect fish populations almost as significantly
as direct mortality. The agency believes that the positive
implications of avoidance are obvious and need not be expanded
beyond the statement that it occurs.
Commen t: There seems to be a disagreement in the interpretation
cJfthe work of Ellis and associates. The American Fisheries
Society, Water Quality Section in "A Review of the EPA Red Book:
Quality Criteria for Water" April 1979, states on page 178:
"The Red Book .criterion is said to be based primarily upon
observations made in the field (mostly those of Ellis and
associates) on the relation between observed dissolved oxygen
concentrations at various sample sites and the variety of fish
species present. The presence of a "well rounded fish
population" was taken as an indication of satisfactory
conditions. Doudoroff and Shumway (1970), pp. 241-247, presented
a detailed summary of the inadequacy of Ellis' conclusions,
citing deficiencies of the evidence upon which those conclusions
were based. It was shown that good mixed fish faunas, as defined
by Ellis (1937), actually can occur in warm waters where
dissolved oxygen concentrations do not exceed 4 mg/liter and
sometimes are as low as 1.4 mg/liter or less. But these
observations do not prove, of course, that fish production is not
seriously impaired in all situations at such low dissolved oxygen
levels."
Response: The agency sees no disagreement with its current
evaluation of field studies (including that of Ellis) and that
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contained in the AFS review of the Red Book. EPA's conclusion
based on these field studies is that they "all indicate that
increase in dissolved oxygen concentrations above 5 mg/L do not
produce noteworthy improvements in the composition, abundance/ or
condition of non-salmonid fish populations/ but that sites with
dissolved oxygen concentrations below 5 mg/L have fish
assemblages with increasingly poorer population characteristics
as the dissolved oxygen concentration becomes lower." Just
because the few field studies all showed effects of dissolved
oxygen below 5 mg/L doesn't mean that good populations of fish
can't exist under conditions of lower dissolved oxygen. The two
positions do not appear contradictory.
Comment; We do not concur with the final Field Observations
conclusion (p. 17) that field study findings are consistent with
the non-salmonid criteria proposed. Bow can the statement that
"increases in dissolved oxygen concentration above 5.0 mg/L do
not produce noteworthy improvements in the composition,
abundance/ or condition of non-salmonid fish populations"
possible be equated to moderate production impairmenmt for early
life stages?
Response; The fact that the field studies did not detect
noteworthy improvements in the fish populations at dissolved
oxygen values above 5 mg/L is not inconsistent with the criteria
conclusion that moderate production impairment could be caused by
early life stage exposure to a constant or mean concentration of
5 mg/L. These field studies emphasized species composition, so a
moderate reduction (eg. 20%) in growth or production would not
necessarily have an impact on species composition. Depending on
a number of factors, including when spawning occurred/ when the
low dissolved oxygen concentrations occurred/ and immigration,
such an effect could be difficult to detect in all but the most
intensive field study.
Comment; Laboratory experimentation, as documented in the
criteria, which determined lethal concentrations at an extremely
low, non-fluctuating level over a relatively long period of time,
simply do not portray the "real world" situation.
Response; EPA agrees, and has made this application to real-
world dissolved oxygen variability a main point in deriving a
two-number criterion approach. Recognition of this factor has
led to the use of constant exposure laboratory data only as an
average field concentration rather than a minimum. The only
exception to this (and the primary point in the above comment)
has been in short term exposures. EPA believes that relatively
constant exposures to very low dissolved oxygen concentrations
can also occur naturally for periods of a few hours to a few
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days/ and that concentrations that can be lethal over periods of
such short duration should never be allowed.
Comment: The document should include a position on the statement
referenced from Doudoroff and Shumway (1970): "...the disposal
of toxic pollutants must be controlled so that their
concentrations would not be unduly harmful at prescribed/
acceptable concentrations of dissolved oxygen/ and these
acceptable dissolved oxygen concentrations should not be
independent of existing permitted concentrations of toxic
wastes." Although toxic substances must be controlled, there
should be no sacrifice of BOD control to maintain adequate
dissolved oxygen to support beneficial uses in the receiving
water.
Response: At the criterion level/ the agency treats each
criterion in virtual isolation. Thus/ dissolved oxygen
concentrations are not considered in setting criteria for toxic
chemicals nor is the presence of toxic chemicals presupposed in
establishing dissolved oxygen criteria. It is entirely
appropriate to caveat the criteria with a discussion of potential
interactions/ or to establish more stringent standards in
recognition of actual conditions of interactive stresses. The
agency agrees with the Doudoroff and Shumway statement in
application of criteria/ but not in establishing criteria.
Comment: We believe that consideration of the daily drsso-lved
oxygen cycle and associated minimum diurnal values is a valid
concern. However/ we believe that existing criteria/ which are
set as an absolute minimum of 5 mg/L to be attained at any time
during the diurnal cycle/ are sufficiently stringent to
adequately protect all aquatic species.
Response: EPA is certain that the diel cycle of dissolved oxygen
is highly variable from place to place and also varies with
weather and discharge factors. The development of a minimum
criterion to apply to situations where diel cycles are large
would not be as protective in a situation where cycles are minor.
A minimum, if high enough/ can be protective in both cases/ but
it can be overly stringent in the case of large cycles.
Conditions that meet a minimum of 5 mg/L may meet or exceed all
the proposed criteria except that for salmonid early life stages.
The critical factor is the magnitude of the diel cycle. If the
dissolved oxygen concentration is very stable/ then a 5 mg/L
minimum is equivalent to a 5 mg/L average and this is presumed to
allow some degree of production impairment for coldwater fish and
early life stages of some warmwater fish. The existence of diel
cycles of dissolved oxygen in the range of 2-3 mg/L, coupled with
a 5 mg/L minimum would meet all criteria except that for salmonid
early life stages.
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Comment: Data presented by EPA in Section II.C. does not support
the assumption that growth in the laboratory and in nature are
equal. Indeed/ data to support such an assumption is entirely
lacking.
Response: EPA has clearly stated its position on the
applicability of the laboratory growth data to field situations:
"The applicability of these growth data from laboratory tests
depends on the available food and required activity in natural
situations. Obviously/ these factors will be highly variable
depending on duration of exposure/ growth rate/ species/ habitat/
season/ and size of fish. However/ unless effects of these
variables are examined for the site in question/ the laboratory
results should be used." There are actually limited data cited
in the criteria document to suggest that effects in the field
might be more severe than in the laboratory (Brake/ 1972), but
the agency believes that situations will be found to contradict
any general statement of applicability or inapplicability.
Comment; An additional flaw should be listed in comparing lab
studies with natural conditions. That is/ natural adaptations
which may have occurred to populations in specific localities.
Behavioral/ physiological/ and morphologic variation is not
uncommon between populations of the same species. In the absence
of evidence to the contrary/ it would no.t be unreasonable to
jeipecTE a"Tiunknown degree of physiological variation due to
evolutionary processes in separate populations of aquatic species
found throughout the various river systems of the nation.
Response: Previous exposure to low dissolved oxygen
concentrations can/ in the short-term/ produce physiological
changes that make a fish more able to function at low dissolved
oxygen concentrations. Similarly, behavioral and morphological
characteristics can be selected for over the course of mutiple
generations. Mixing of game-fish stocks will confuse the issue,
and tests with stocks of unknown or questionable genetic history
would yield results of uncertain applicability. From a site-
specific standpoint the agency would support modification of
criteria based upon reasonable demonstration of biogeographic
differences in sensitivity to low dissolved oxygen. Such tests
should carefully differentiate between short-term acclimation and
genetic selection/ and should show a reasonable degree of
generalization to a number of species at the site. EPA knows of
no way to establish criteria based upon an unknown degree of
physiological variation.
Comment; The dosing model discussed in the document is indeed
tentative and theoretical. This discussion is based on data from
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several apparently independent and unrelated studies which
generated results difficult to compare (Section. II.C. page 5/
paragraph 1). The variety of results were apparently pooled and
then compared to control growth rates by mathematical means.
The known growth rates used as the control are of
questionable value. Control growth rates were derived from a
single laboratory study utilizing a number of species and a
limited number of replicates (n=l to 12, page 5, Table 1). No
evidence is provided to demonstrate the control growth rates
would compare to the wide variety of conditions found in nature.
Response; The dosing model discussed was based on fluctuating
exposures/ and their relationship to continuous exposures/ in
largemouth bass. These are not the data in Section II.C.
(Salmonid Growth). And these salmonid growth data were pooled
only after normalization to the appropriate control within each
test. No single growth rate can compare to a wide variety of
growth rates; such a conclusion is obvious.
Comment: Deleting values above 6 ppm based on the data presented
seem unwarrented. EPA states that..."apparent reductions in
growth rate sometimes seen above 6 mg/L are not usually
statistically significant"(Section II.C./ page 6/ paragraph 1)
implying that at least some test results are indeed significant.
If a mean concentration level is used as a basis for standards/
it would logically be a mean of true conditions/ not a mean
artificially derived by eliminating a potentially substantial
portion of data collected to establisah such a mean. EPA states
that using the procedures described in this paragraph..."growth
effects appear to be a reasonable function of the mean"... The
"appearance" of such a relationship may be misleading. A true
relationship is no,t clearly demonstrated in this discussion.
Response; EPA analysis of the largemouth bass data of Stewart et
al.(1967) is the basis for the statement regarding 6 mg/L and
deriving averages that predict growth effects. These data and
their discussion have no direct relationship to the statement in
Section II.C. regarding salmonid growth. With respect to the
largemouth bass study/ EPA agreed with the authors' conclusions
as far as the authors went. That is/ the mean dissolved oxygen
concentration was not a good indicator of effect on growth
(underestimating effect) and that the use of the minimum provided
a better estimate of effect (but an overestimate). Stewart et
al. observed no effect in constant exposures to dissolved oxygen
concentrations above 6 mg/L. The agency hypothesized that if
similar growth would occur at 6, or 8/ or 10 mg/L/ then using
values above 6 mg/L would inflate the mean dissolved oxygen
concentration so that it would underestimate the effect on
growth. This is exactly what the authors observed. This
suggested that treating periods above the 6 mg/L threshold as if
16
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they were actually 6 mg/L should yield a better predictor of
effect on growth. Trying this concept with the data of Stewart
et al. provided the agency with an average concentration of
dissolved oxygen that gave a good estimate of the growth
obvserved. Providing graphical example of the various types of
analysis with the data of Stewart et al. would require at least
three figures/ and the agency decided against including these in
the criteria document.
Comment; Even though a "square wave" variety of exposure is
distinctly different from a sinusoidal pattern which would be
expected in nature/ such patterns may likely represent the
sinusoidal characteristics more accurately than "constant
exposure" experimentation/ which is clearly uncharacteristic in
nature/ at least in the major river systems of the west.
Response; Exactly! That is why the agency has used "square
wave" data from studies like Stewart et al. in deriving the
averaging concept applied in these criteria. Although limited/
they provided a reasonable estimate of more natural sinusoidal
cycles. Using constant exposure data would provide no mechanism
for developing a dosing model for cycling dissolved oxygen
concentrations. Constant exposure data were used primarily in
developing the "levels of impairment" estimates which were then
modified by the cycling exposure model to provide the criteria.
Comment; In discussing naturally-occuring dissolved oxygen
levels EPA clearly implies that concentrations lower than
criteria are a natural phenomenon under which fish and other
aquatic organisms have evolved. Indeed/ the statement is made
"These naturally occurring conditions represent a normal
situation..." -Y-et? EPA continues by .stating. .. "Under these
circumstances the numeric criteria should be considered
unattainable/ but naturally occurring conditions which fail to
meet criteria should not be interpreted as violations of
criteria." The paragraph further asserts that natural conditions
should be compared to natural ambient conditions and not to ideal
conditions. It seems paradoxical that EPA chooses to promulgate
criteria in order to meet some ill-defined ideal condition
determined through the comparison of flawed data rather than to
emulate natural conditions under which species evolved.
Response; EPA believes that criteria (or standards) should
recognize natural concentrations and attainability. This does
not mean that criteria intended to describe levels for protecting
aquatic life and its uses should ignore effects that occur when
dissolved oxygen concentrations fall to levels that produce
adverse effects simply because natural populations exist
elsewhere at those levels. EPA generally agrees with the
statement of the AFS Red Book review committee: "It was shown
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that good mixed fish faunas, as defined by Ellis (1937), actually
can occur in warm waters where dissolved oxygen concentrations do
not exceed 4 mg/liter and sometimes are as low as 1.4 mg/liter or
less. But these observations do not prove, of course, that fish
production is not seriously impaired in all situations at such
low dissolved oxygen concentrations."
Comment; A more focused discussion of the effects of temperature
on dissolved oxygen requirements should be provided, one that
contains none of the contradictions that appear to confuse the
proposed document.
Response: The only potential contradiction we see in the
discussion of temperature effects deals with the greater
sensitivity of coldwater salmonids than warmwater fish. We have
added a phrase to specify that growth effects of low dissolved
oxygen are more severe as temperature increases "along the range
tolerated by each species." Thus, it is not inconsistent to find
a greater effect on the growth of trout at 20 C than of
centrachids at 25 C.
Comment: Data presented in the discussion do not adequately
define periods of high growth rate, upper temperature levels, or
pollutant levels which present near-toxic conditions. The
paragraph discussing these factors is ambiguous and rhetorical.
Response; The subject statement is intended as a qualitative
warning to the reader of the criteria document. Attempting to
quantify stressful levels of temperature and toxic pollutants as
well as defining periods of high growth rates would be
impossible. These factors would vary from species-to-species,
from site-to-site, and with countless combinations of stressors.
v • -'.
Comment; The criteria document speaks to the synergistic effect
of the presence of chemicals, pathogens and temperature at
slightly stressful levels and what might otherwise be acceptable,
but borderline, dissolved oxygen concentrations. The approach
should be to address the problems associated with these stressful
levels of chemicals, pathogens and temperatures where practical;
not to set unrealistically high dissolved oxygen requirements.
Response; The dissolved oxygen criteria have not used a safety
margin of any type other than to establish criteria that would
apply at temperatures typical of seasonal highs .that are
representative for appropriate species and life stages. If
disease or other pollutants are present at levels more stressful
than those in the tests upon which the criteria are based, then
the criteria would be less protective. The agency simply wishes
to emphasize that when these other stresses are known or
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suspected to be significant it is most important to meet the
criteria. Failure to do so could have more severe effects than
those outlined in the criteria document. The choice of how to
most effectively and economically reduce multiple stresses is not
within the scope of the criteria document. The coramentor should
appreciate a parallel statement that stressful dissolved oxygen
concentrations should be addressed rather than set unrealistic
requirements for chemical discharges.
Comment; The criteria document should more explicitly link the
threshold dissolved oxygen cnncentrations used in the impairment
rankings with particular research and species. This would
enhance the use of Ithe criteria on a site-specific basis by
providing a more objective means of considering species-specific
criteria by omitting nonresident species, or life stages (in the
case of put-and-take fisheries).
Response; The criteria are based on species group
generalizations/ not on a basis that lends itself to simple
species-by-species reformulation. For example, EPA believes that
the salmonid criteria are general to all salraonids, and that any
apparent differences in sensitivity between species are just as
likely to be the result of experimental variables other than
dissolved oxygen concentration. Such variables would include
test temperature, size and age of test organisms, and feeding
regime. The site-specific flexibility tor life stages is already
built into the criteria by having separate criteria for early
life stages and other life stages. The agency doubts that the
warmwater criteria, based largely on the data in Figure 1 (early
life stages) and Table 4 (other life stages), are amenable to
simple species deletion calculations. This belief is founded on
the observation that the entire data base in these two summary
presentations include only nine species out of some 600
freshwater species.
It should be possible to support a lower standard for other
life stages of yellow perch if they are the only species present
because the sensitivity of yellow perch appears to be less than
that for the other species shown in Table 4. Where other species
for which there are no data are present, it could be extremely
difficult to infer the appropriate surrogate species (or genus or
family) from those for which data exist. The necessarily more
subjective nature of the warmwater criteria was discussed in the
Introduction of the criteria document.
Comment: The production impairment levels given in the document
are arbitrary and based on judgement, generalization, and
assumption. Therefore, it appears that there is no valid
scientific basis for the impairment levels given. Consequently,
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we would recommend that these impairment judgments be removed
from the criteria document since they might be misconstrued and
given more credence than they merit. In fact, it is hard to see
how they would be used in criteria formulation since the
impairment levels are divided into salmonid and nonsalmonid
waters which differs from the criteria basis.
Response: The agency agrees that the impairment level values are
based on judgement/ generalization/ and assumption. The
assumptions and generalizations are discussed in the text and the
data used in formulating these judgements are discussed in
reasonable detail and cited. The agency does not believe that
the resultant levels are arbitrary. However/ additional
explanation will be added to provide the reader with the
assumptions made and emphasizing the advisory nature of these
values. The fact that the impairment level estimates are divided
into salmonid and nonsalmonid categories should pose no more
problem than the local decision of which, if any/ coldwater and
coolwater nonsalmonids should be protected by the coldwater
criteria.
Comment: Attempts to define effects on growth at various
dissolved oxygen concentrations are well taken. Doing so
provides state regulatory agencies a greater opportunity to
define desired levels of protection in individual receiving
waters. Even though state regulatory agencies may exercise the
opportunity to define desired levels of protection, the propriety
of the criteria now suggested are no less significant since many
agencies will not have the expertise available to re-interpret
the available data for each situation.
Response: The growth data are the primary basis for the criteria
for other life stages and form the bulk of the documentation for
the levels of impairment estimates in the document. The agency
intends for these data and conclusions to play a role in
evaluating the adequacy of standards and in their modification
following evaluation of use attainability, socio-economic
factors, and risk assessments. As stated in the preceding
response/ these numerical values are based on judgement,
generalization, and assumption; local application may be tempered
by new information/ knowledge of site-specific biology, or many
other factors. The criteria should not be modified simply
because they are imperfect. The agency appreciates the statement
of support for the inclusion of the growth data summaries.
Comment; The document appears to provide a thorough review of
the available data. It also provides a useful conclusion section
through the qualitative descriptions of impairment for various
life stages. This will aid states in their selection of
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applicable criteria particularly when the salraonid larval life
stage is not present in the streams.
Response; The guidance for flexible application of the document
is one of the primary reasons for providing an updated criteria
document as we stated at the first of this reponse to public
comment document.
Comment: The 3 mg/L threshold for salmonid early life stages
identified in the criteria document is assigned as the acute
mortality level/ completely contrary to and unsupported by the
data presented.
Response; The 3 mg/L value given for the acute mortality limit
for embryonic and larval stages is both conditional and
judgemental. As long as respiration is largely passive/ lethal
dissolved oxygen is greatly influenced by flow. At low flow
rates common to many intergravel environments 3 mg/L would be
capable of producing lethality. As shown by Eddy (1972) at high/
but tolerable/ incubation temperatures and high flow rates
survival of chinook salmon was reduced at dissolved oxygen
concentrations below 7 mg/L. These factors plus the fact that
dissolved oxygen concentrations between 2 and 3 mg/L can be
lethal to juvenile salmonids make it prudent to declare a 3 mg/L
threshold for avoiding lethal effects on embryos and larvae.
With .the 3 mg/L differential between intergravel and overlying
waters this results in a 6 mg/L water column criterion. At cold
temperatures and good flow rates this may be higher than
necessary/ but at warmer temperatures and slower flow rates even
this may not be adequate.
Comment; The dissolved oxygen concentrations judged to be
equivalent to stated qualitative levels are not supported by the
criteria document. Evidence supplied by EPA strongly indicates
that the proposed dissolved oxygen levels are substantially
greater than the data indicate are necessary. EPA cites several
studies (Brannon, Chapman and Shumway) indicating that continuous
exposures down to 3 mg/L resulted in only minor decreases in
weight attained by salmon and steel head larvae provided adequate
flow is available. Yet/ the proposed dissolved oxygen
concentration levels lead one to believe that concentrations 2 to
3 times that level are necessary to avoid production damage.
Response: Although little effect on size at hatch is seen in
laboratory studies at high water flow rates and 3 mg/L/
considerable effect is seen at lower flow rates/ including delay
in hatching and smaller size at hatch. Moreover/ available
evidence indicates about a 3 mg/L difference between intergravel
dissolved oxygen and overlying dissolved oxygen. A new study has
just been published that suggests that 6 mg/L in the intergravel
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water may reduce the survival of early life stages of salmonids;
the agency is still evaluating this study. In addition/.the
studies cited in the comment did not include effects on feeding
and growth/ merely yolk utilization and growth. Since growth
resulting from external food sources is affected at 5 mg/L in
older salmonids it is likely that growth of larvae would be
similar in sensitivity. All these factors suggest that a minimum
dissolved oxygen concentration in the intergravel environment
should be about 6 mg/L and that to achieve this would require an
additional 3 mg/L in the overlying water column.
Comment; While we are in agreement with the need for more
stringent criteria for coolwater fish/ the document/ after
initially bringing the subject up appears to abandon it and
discuss the coolwater and warmwater fish as a single unit.
Response: State agencies and biologists probably have different
terminologies and lists for what constitutes cold-/ warm-, or
coolwater fishes or habitats. Where defined in regulations/ more
often than not/ water temperatures are mentioned rather than
species. Few states use a coolwater category/ using instead a
coldwater-warmwater dichotomy. The present criteria format is
intended to allow the states themselves to define what they
consider as coldwater species (ie. species to be protected by the
coldwater criteria).
Comment; The agency needs to further clarify its position
concerning 1) which species (ie. northern pike/ etc.) would be
considered coolwater organisms/ and 2) how many coolwater species
must be present for a stream to be considered as a coolwater
stream.
Response; EPA be-lieves that no preset number of species in a
more sensitive category can be used in categorizing a stream as
coldwater or warmwater. A stream with an excellent self-
sustaining brown trout fishery may contain only one coldwater
species but probably should be protected by the coldwater
criteria. A put-and-take trout fishery might be protected by a
standard below the coldwater criteria. The agency believes that
the data are not sufficiently robust to define which species
belong' in the coldwater category in addition to salmonids. The
user of the criteria is encouraged to evaluate the available
biological and temperature data and current use categories for
the waters in question. From a regulatory standpoint/ the agency
is opposed to adopting rigid species lists of cold- or coolwater
species at this time.
Comment; The proposed criteria document defines early life
stages to include "all embryonic and larval stages and all
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juvenile forms to 30-days following hatching." This definition
is so broad that almost all surface waters could be included in
the ELS scope for substantial portions of the year, including the
critical low dissolved oxygen period of late summer-early fall.
This is the case irrespective of whether or not the spawning
activity is significant in the overall productivity of the
fishery. The EPA should provide clear guidelines delineating
those significant spawning activities for when the ELS criteria
would be appropriate to include as a standard on a site-specific
basis.
Response: The agency realizes that in many waters the early life
stage of one-or-more species will be present during all, or most,
of the critical period of low dissolved oxygen. Under these
conditions the early life stage criteria would apply unless a
state had sound reason to believe that such a concentration of
dissolved oxygen was unnecessary to the protection of the aquatic
life. EPA wishes to point out that the minimum for early life
stages is 5 mg/L, the same as that in the current Red Book
criterion, so that protecting early life stages with a year-
around minimum of 5 mg/L constitutes no change in the minimum
from current criteria. The currently proposed criteria do
however allow for less restrictive warmwater criteria when early
life stages are not present.
Comment; The differentiation between early life stages and other
life stages is a needed improvement over the existing criteria.
However, we feel this concept would be more usable if EPA could
better define how the breakpoint should be derived.
Response: Analysis of the available data on the relative
sensitivity to low dissolved oxygen of spawning and embryonic
and larval development strongly suggests that the larval forms
are often the most sensitive. Sometimes the embryonic stages are
most sensitives, but there is no indication that the act of
spawning per se_ is as sensitive (but there is really little data
on the effect of low dissolved oxygen on spawning behavior).
It therefore appears necessary to provide for dissolved oxygen
concentrations that are protective of these more sensitive early
life stages. In fact, many early life stage tests include not
just embryonic and larval forms, but also early feeding stages
that are technically not larvae but post-larval juveniles.
The agency is unable to establish species-by-species
schedules of development and sensitivity to guide the user. EPA
believes it is important that the user of the dissolved oxygen
criteria realizes that spawning may not often be the activity
that requires the highest dissolved oxygen concentration, but.
rather it is the embryonic and post-hatch stages (both larval and
nonlarval). The 30-day post-hatch period is included in the
early life stage definition because it avoids complex
23
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morphological descriptions or definitions that are not paralleled
in experimental designs of research anyway. There is probably no
cook-book formula that can pin-point the time or stage when the
sensitivity of very young juveniles transforms to the sensitivity
of older fish. In most cases there is probably a more-or-less
gradual decrease in sensitivity. The use of a 30-day post-hatch
period is consistent with the period used for the duration
standard defining an acceptable early life stage test for
toxicity evaluation.
Comment; It is difficult to compare the new criteria
recommendation with the present state standard of 5 mg/L that is
currently interpreted and used in large stream modeling as a
cross-sectional average, daily minimum. Average diel swings are
analyzed and daily average dissolved oxygen concentrations
targeted at 5 mg/L plus one-half of the average diel dissolved
oxygen swing to calculate allowable BOD loading. Use of a mean
of 5.5 mg/L as proposed in the warmwater category would be less
restrictive to waste load allocation, but during May, June and
possibly July the 7-day mean of 6 mg/L for early life stages
would likely apply and be more restrictive than our current
modeling process.
Response: The comparison of the new criteria with current
practices depends primarily on the magnitude of the diel cycle.
For other life stages of warmwater fish the new criteria are less
restrictive on waste loading if the cycle exceeds 1 mg/L and are
more restrictive if the cycle is less than 1 mg/L. Conversely,
if the diel swing exceeds 1 mg/L the current 5 mg/L minimum would
be slightly more protective than the proposed criteria. Also,
with a diel cycle less than 1 mg/L the current 5 mg/L standard
could allow what has been estimated as "slight production
impairment." In general, the agency believes that a 5 mg/L
minimum at any time provides conditions that will meet or exceed
the proposed criteria for other life stages of warmwater fish.
Through similar calculation, the early life stage criteria
are more restrictive than a simple 5 mg/L minimum if the diel
cycle is less than 2 mg/L, but is the same as a 5 mg/L minimum if
the diel cycle is greater than 2 mg/L.
Comment: Most spring and summer nonsalmonid spawners do not bury
their eggs in gravel nests, yet these would likely be grouped
with salraonids as sensitive species, causing the waters in which
they spawn to be subject to the much more stringent coldwater
early life stage criteria. If the critical factor in these
extremely high values is the differential needed for protection
of eggs buried in gravel, then separate criteria should be
established only for salmonids and those nonsalmonids that also
24
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lay their eggs in gravel nests. Sensitive nonsalmonids that do
not lay eggs in gravel nests should be evaluated to determine if
a separate criteria should be developed to apply to the spring
and summer months in which they spawn.
Response; Note that the criteria state: "For species [of
coldwater fish] that have early life stages exposed directly to
the water column/ the figures in parentheses apply." The early
life stage criteria for warmwater and coldwater fish that do not
bury eggs in gravel are almost identical; both have a minimum of
5 rag/L, and the averages are 6.0 mg/L and 6.5 mg/L for warmwater
and coldwater species/ respectively.
Comment: The proposed 1-day minima should be shown as
instantaneous values.
Response: The 1-day minima were not called instantaneous minima
because of implications of continuous monitoring. Indeed/ in-so-
far as they are values to met at all times they are instantaneous
values. The discussion of calculation of daily means in the
National Criterion section and shown in Table 7 should make it
clear that the daily minimum is an instantaneous value. However/
a footnote - could be added to the criteria table making it clear
that this is an instantaneous minimum. The agency believes this
approach is preferable to possible confusion between the
instantaneous minimum and the 7-day mean minimum (which is the
average of the instantaneous minima from seven consecutive days
and not to be construed as a minimum of seven consecutive daily
averages).
Comment: As the guidance currently stands/ the rationale for the
recommended levels is not fully explained/ and therefore
questionable. . 'For instance/ why weren't the criteria based on
the "no production impairment" levels presented and discussed on
pages 24-25? Why was a safety factor of 0.5 mg/L applied to the
average criteria as discussed on page 25 and not applied to the
1-day minimum? We prefer to develop water quality criteria based
on most sensitive species and apply safety factors through the
calculation of effluent limits.
Response: The problem of establishing no-effect concentrations
is well-recognized in toxicology where such estimates are a
function of statistical confidence levels and curve fitting
techniques. The "no production impairment" concentrations listed
in the document are based primarily on the growth data in Tables
I/ 2, 3, and 4 and the survival data in Figure 1. The various
impairment values can, for example/ be interpolated from selected
growth reduction percentages that are reasonably consistent
regardless of the curve fitting model chosen. The "no effect"
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values on the other hand are extremely dependent upon the model
selected. The 0.5 mg/L added to the slight production impairment
values was a conscious effort to provide a criterion that
provides for less than a slight effect/ but not a criterion that
is based upon a more subjective and ill-defined "no-effect"
estimate.
The approach used is viewed by the agency as being
equivalent to the approach used in establishing toxicity
threshold concentrations by taking the geometric mean between
upper and lower chronic concentrations. Thus/ the 0.5 mg/L is
not a "safety factor" but rather a threshold estimator for
interpolating between a concentration that is known to produce a
slight effect and a concentration believed to be a conservative
"no effect" estimate.
Comment: Background information is lacking in the derivation of
1-day minimum criteria for the early life stages of coldwater and
warmwater species. The relationship of criteria associated with
"sub-acute lethality" to values thought to result in acute
mortality or other levels of impairment deserves elaboration.
Accordingly/ the Agency is urged to assemble that information and
subsequently make it available for public review.
Response: The 5 mg/L 1-day minima for early life stages of fish
is the least-documented of the criteria. Comparisons with the
values in the Production Impairment section show a degree of
conservatism not evident in the other dissolved oxyigen criteria.
This conservatism is based upon several factors. For salmonids/
these include the potential of brief exposure to low dissolved
oxygen concentrations triggering simultaneous early hatching
with its unknown effect on survival/ the apparently significant
interaction of sl-ight reductions in dissolved oxygen and high
temperatures on embryo and larval survival/ and the uncertainty
of intergravel flow rates. For nonsalmonids, the uncertainty
involves the duration of exposure to low dissolved oxygen
concentrations required to produce the mortality seen in the
early life stage studies summarized in Figure 1. Was this
mortality a cumulative phenomenon or did it occur at some rather
brief period of great sensitivity? As a result of these
uncertainties, the agency deemed it prudent to select what might
be a conservative instantaneous minimum of 5 mg/L because this
concentration represents a safe concentration with perhaps only a
slight margin of error and because 5 mg/L is consistent with the
Red Book criterion.
Comment; We believe that the nonsalmonid data for particular
species is too limited and sometimes too conflicting to support
the proposed criteria revision. For example/ channel catfish/
which are ubiquitous in this state/ have a variable breeding
season from March through July. Under the new proposal/ the 6.0
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mg/L early life stage criterion would be in effect during most of
the critical warm months in the state. Typical dissolved oxygen
saturation values during these months range from 7.5 to 8.0 mg/L.
Clearly/ natural conditions/ particularly during early morning
hours/ would violate the proposed criterion in many streams.
Furthermore/ we can find no data or evidence to indicate the the
states current 5.0 mg/L dissolved oxygen criterion results in
impairment of or detrimental effects on channel catfish
reproduction/ different life stage growth and survival, or
behavior. In addition to channel catfish/ numerous other
important species (shad/ shiners/ sunfish) exhibit extended
breeding seasons from May through September. The applicatin of a
6.0 mg/L early life stage criterion to these species is also
considered dubious.
Response: Explicit in the criteria document is the principle
that natural conditions may fall below the proposed criteria but
can not be viewed as "violating" criteria (especially in-as-much
as criteria are not standards and hence cannot be violated in a
legal sense). The agency recommends that when natural conditions
are below criteria that further reduction be limited to a 10%
reduction below the natural conditions. Any state which meets an
instantaneous minimum 5 mg/L standard clearly meets all proposed
warmwater minima/ almost certainly meets the 30-day mean/ and
given daily or weekly maxima near 7 mg/L they will also meet the
7-day mean of 6 mg/L for early life stages.
Comment; The 3.0 mg/L one day minimum is inadequate to protect
fish and other aquatic biota. This one day minimum figure is
especially critical as the remainder of the criteria is expressed
in terms of "mean" figures which is a concept that we find
unacceptable. Setting the one day minimum at what is described
as the "Acute Mortality Limit" and below what we consider as a
level suitable for fisheries management/ leaving no safety margin
at all for avoiding stress/ fish kills/ etc. is also
unacceptable.
Response; The 3.0 mg/L concentration is one that will rarely/ if
ever/ be attained. For most discharges/ waste load models (eg.
the 7Q10 approach) would/ except in extremely rare cases/ be
driven by the 7-day mean minimum for other life stages or the 5.0
mg/L minimum for early life stages. Under these circumstances it
is unlikely that the instantaneous minimum would ever approach
3.0 mg/L. Never-the-less/ in rare situations/ a deviation below
5 mg/L to near 3 mg/L would not be expected to produce acute
lethality. This is the same concept the agency follows with
criteria for toxic pollutants and is the general concept behind
all 2-number (mean and extreme) criteria in general. The sample
calculations given in Table 7 should make it clear that the 7-day
mean minimum functions much more as a minimum than as a mean.
The agency believes that a simple 5 mg/L minimum criterion gives
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the false impression that deviations below 5 mg/L will result in
adverse effects in all aquatic systems; in fact/ there is no
evidence to support this general conclusion. Additional
stipulations are given in the criteria document for application
where manipulable discharges might be able to reach the 1-day
minimum with routine regularity.
Comment; Considering the water quality criteria on the basis of
"mean" concentrations provides inadequate protection for aquatic
life unless the one day minimum is set at a level sufficient to
accomplish this protection.
Response: This is exactly what the agency intends to achieve
with the combination of the 7-day mean minima and the
instantaneous minima.
Comment; When it comes to the "bottom line", i.e. the "one day
minimum/" the subject of coldwater/ coolwater and warmwater is
academic as all fish are treated equally. This is unacceptable.
Response; The agency realizes that considerable variation exists
in the acute tolerance of various species to low dissolved oxygen
and that the lethal threshold for many warrawater species may be
considerably lower. But because of the lack . of data for most
warmwater species and the existence of a wide variety of
conditions, the agency generally recommends against allowing
deviations below 3 mg/L.
Comment; The criteria propose a one day rainmimum dissolved
oxygen concentration of 5.0 mg/L for early life stages and 3.0
mg/L for other life stages of nonsalmonid fishes. Under worst
case conditions with a sustained minimum of 3.0 mg/L, there would
probably be no fish kills in most waters; however, this low
dissolved oxygen concentration would favor nongame fish (gar,
bowfin, and carp) over game fish (pickerel/ bass, and bream) and
lead to development of an imbalanced population.
Response; It is highly unlikely that a sustained minimum of 3
mg/Lwould ever occur. Such an occurence would be severly
limited by the 7-day mean minimum (see response immediately
above). Where dissolved oxygen concentrations are significantly
raanipulable by dischargers, the agency recommends a 4 mg/L
mini mum.
Comment; As soon as this document was available and dischargers
reviewed it, nearly all attention focused on the 3 mg/L value.
Even though the other values are also an important part of the
criteria, the 3 mg/L value was brought up as a suggestion that
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our current criterion (5 mg/L) was too stringent. We hope the
EPA appreciates the problems caused when these "simplifications"
are brought before policy boards and agencies. The perception
that this new criteria is a relaxation from past recommendations
must be countered to the maximum extent possible. Further/ the 3
mg/L value is identified as an acute mortality limit which means
that the recommended criteria condones such an effect.
Response; The agency appreciates the fact that persons not
familiar with the concepts behind the new criteria would have a
tendency to misinterpret the significance of the 3.0 mg/L
minimum. The agency finds it hard to believe that such
misinterpretation would persist following a simple explanation of
the other facets of the criteria. In fact/ the allowance/
however constrained/ to allow dissolved oxygen concentration to
ever drop to 3 mg/L does reflect the possibility that higher
minima are more restrictive than those EPA now proposes as
tolerable. EPA believes the 7-day mean minimum is easily more
restrictive than the 3.0 mg/L instantaneous minimum in a modeling
sense/ and can be compared directly to current 7Q10 models (based
on daily minima but not on daily means). The 3.0 mg/L minimum
merely puts a floor under the operational criteria that are based
on means of one type or another.
The 3.0 mg/L minimum is not expected to cause acute effects
and such effects are not condoned. The agency will consider
changing the term in the production impairment section
from "Acute Mortality Limit" to "Limit to Avoid Acute Mortality."
However/ the document already states: "the value cited as the
acute mortality limit is the minimum dissolved oxygen
concentration deemed not to risk direct mortality of sensitive
organisms."
Comment: It is suggested that the one day minimum criteria for
warmwater fish (dther life stages) be reconsidered to at least
4.0 mg/L. Setting the level at the potentially acute mortality
level for sensitive species seems to be defeating the intent of
the criteria. This is self-defeating when data indicates toxic
effects from ammonia are increased at low dissolved oxygen
levels. These higher ammonia and lower dissolved oxygen
conditions are likely to occur below most wastewater treatment
facilities. Therefore/ either wasteload allocation processes
must account for this synergistic effect in lowering the
allowable ammonia discharge or the state dissolved oxygen
criteria must be selected at a higher level to prevent the toxic
cndition.
Response: The agency has always believed that water quality
criteria (not standards) should provide a summary of effects and
effect concentrations for the subject parameter. To establish
criteria for worst-case combinations of factors would make it
extremely difficult to apply criteria to the myriad of less-
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stressful environments. Rather/ any such interactions (such as
the potential interaction of ammonia and low dissolved oxygen
concentration) should be considered in the standards-setting
process. This procedure allows for site-specific factors to be
brought into consideration at the simplest level/ not with a
criterion that has been altered by considerations of some
potentially complicating factors that may or may not be present.
Temperature, which is usually a natural rather than anthropogenic
complication/ is the only exception to this restriction in the
dissolved oxygen criterion. The proposed criteria have been
established with the assumption that they will be protective at
temperatures in the upper half of the tolerable range for any
given life stage and species.
Comment: Data on the effects of fluctuating dissolved oxygen
concentrations on channel catfish, which should be more
representative of natural aquatic system behavior than tests
under conditions of constant dissolved oxygen, do not, in our
opinion, support the early life stage criteria proposed for
warmwater fish.
Response: Data on the effects of fluctuating dissolved oxygen on
channel catfish were cited from Carlson et al. (1980). These
data are from tests with fish that are of sufficient age to be
considered other life stages rather than early life stages, and
therefore their agreement or disagreement with the early life
stag_e criteria is largely irrelevant.
Comment: In our small stream modelling and effluent limit
calculations, Q7/10 stream conditions, discharge design
conditions, and upstream dissolved oxygen concentrations of 7
mg/L and a minimum downstream dissolved oxygen concentration of 5
mg/L is used to calculate weekly average limits. Since the
limits are based on a weekly average/ the 5 mg/L dissolved oxygen
criterion is a 7-day mean minimum. Shifting to a 4 mg/L 7-day
mean minimum for warmwaters would result in significant impacts
in our environmental protection program.
Response: If the state can support a 5 mg/L minimum/ this
standard that is more stringent than the criterion is certainly
acceptable to EPA. Obviously a change to a 4 mg/L minimum from a
5 mg/L minimum would result in significant impacts in your
environmental protection program. The question is/ would such a
change have a significant impact on the fish and other aquatic
biota?
Comment; The implementation of BOD wasteload allocations and a 5
mg/L dissolved oxygen criterion in several rivers have resulted
in substantial water quality benefits in those rivers. The
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fisheries in those rivers has substantially increased and
diversified/ and sport fish now populate areas where few or only
rough fish existed previously. Local researchers have concluded
that indeed the comeback in these fisheries is attributable to
the improved oxygen and that 5 rag/L appears to be a significant
value in the difference between a poor and good fishery.
We believe the proposed criteria go too far in compromising
the goals and objectives of the Clean Water Act. Too many
arguments are made [in the document] to discount the validity of
data or to interpret the data in a manner designed to produce an
artificially low value which may not be protective of the most
sensitive species. The document/ we believe/ does not
scientifically support the criterion which has been recommended
and we believe a substantial revision is necessary.
Response: -The 4 mg/L 7-day mean minimum for warmwater fish is
indeed lower than the 5 rag/L minimum -standard in place in your
state. The significance of the difference depends first upon the
magnitude of the diel cycle of dissolved oxygen. As mentioned in
a response to your question discussed earlier/ if the diel cycle
is 1 mg/L or less/ the 5.5 mg/L 30-day mean would make the
proposed criteria more restrictive in many instances than the
current 5.0 rag/L minimum. Moreover/ any state standard more
stringent than the proposed new criteria would be acceptable
if supported by site-specific data. The fact that a 5 mg/L
minimum was successful in rehabilitating the fisheries in your
streams doesn't prove that a 4.0 mg/L minimum and a 5.5 rag/L 30-
day mean wouldn't also be successful.-
In discussing a study of such streams/ Coble (1982) has
stated: "Moreover/ with a measure of DO concentration of daytime
or average values/ the level of 5 mg/L could be identified as a
point of departure between good and poor fish populations as they
were defined" [emphasis added]. EPA has proposed a 5.5 mg/L
average dissolved oxygen concentration and an even higher 6.0
mg/L average during early life stages. The agency believes that
these proposed criteria will be protective of all species whose
sensitivities are known. Fine points of detail regarding diel
cycles and averaging periods will show some differences in
application of a 5 mg/L minimum standard and the proposed new
criteria; EPA believes these differences are minor and the
protection afforded will differ very little regardless of which
approach is used.
Comment; The third condition for allowing a lower than
acceptable minimum dissolved oxygen concentration should be
changed. It states that..."minima lower than acceptable constant
exposure levels are tolerable so long as:...3. the minima are not
unduly stressful and clearly are not lethal." How does one
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measure in a river whether "the minima are not unduly stressful"?
Suggest using "not lethal".
Response i The allowance of dissolved oxygen concentrations that
are harmful but not lethal is inconsistent with the goal of water
quality criteria. The proposed criteria provide the user with
estimates of dissolved oxygen concentrations that are considered
not unduly stressful.
Comment; The proposed criteria states that "characterizing the
shape of the [DO] cycles requires several appropriately spaced
measurements." This is too loose a definition. The daily cycle
in many systems/ especially highly productive waters/ can have
sinusoidal cycles some days and nonsinusoidal cycles other days.
To be accurate/ the mean dissolved oxygen concentrations should
be calculated on a time-weighted basis. Unless previous data
suggests little diurnal variation in dissolved oxygen during
critical times of the year/ dissolved oxygen/ at a minimum/
should be measured every two hours (12 per day). To eliminate
any ambiguities/ the means (30 day/ 7 day and 7-day minimum)
should be defined as moving averages.
Response: Compliance monitoring or modeling data should have a
level of resolution consistant with the known or expected extent
of the problem. In areas where compliance may be difficult and
where potential effects are most significant continuous monitors
may be desirable. In less impacted areas a few days or weeks of
high/low estimates may provide all the information needed to
adequately define conditions. The agency must take into account
the resources of those using the criteria? where current
monitoring for compliance with a 5 mg/L minimum amounts to
monthly or weekly sampling/ it seems unlikely that widespread use
of continuous .or > 2-hour sampling frequency are realistic
expectations.
You are correct in the statement that moving averages are
appropriate/ and the agency will specify that approach in the
final document.
Comment: The statement that determining the magnitude of daily
dissolved oxygen cycles requires at least two measurements daily
should be further specified by stating that these two
measurements must be taken at appropriate expected minimum and
maximum dissolved oxygen periods. The time of day/ fertility of
the water/ and season are important in determining when sample.s
need to be taken to adequately characterize dissolved oxygen
cycles.
Response; The agency agrees that the timing of two-a-day samples
Tsimportant and have stipulated that a "reasonable daily average
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is calculated from the day's high and low dissolved oxygen
values." Site characteristics will, of course, make the timing
of the highs and lows somewhat variable, although in most
instances dawn and raidafternoon samples should provide adequate
data.
Comment; Overall/ the document is well written and appears to
encompass a thorough review of available data on the effects of
dissolved oxygen to aquatic life. We are particularly pleased to
see that it recognizes that coldwater and warmwater fishes, as
well as their respective life stages, have different dissolved
oxygen requirements. The use of a two-concentration criterion,
comprised of both a mean and a minimum, is also good, since it
recognizes that chronic effect limits can be safely exceeded for
short periods as long as a mean concentration is maintained.
Response; The agency is pleased that the more flexible format of
the new dissolved oxygen criteria has your support.
Comment; We fundamentally oppose any requirement for a dual or
mutiple-level classification system for coldwater, coolwater, and
warmwater species simply because other states utilize such an
approach. Highly variable conditions of hydrologic behavior and
temperature, biological production and species existence, and
natural pollutant loadings in different regions of the country
make the establishment of the revised nationally uniform system
indefensible and ill-advised. If new criteria need to be
established, we would favor regional criteria, which would allow
consideration of differing natural physical conditions, as a
preferable alternative.
Under our current water quality standards rule covering
aquatic life use./'.one of four freshwater habitat ratings can be
assigned as a designated use for classified waters. The system
relies on different absolute minimum dissolved oxygen
requirements for each quality level of freshwater habitat. For
example, waters with a put-and-take trout fishery are assigned a
6.0 mg/L criterion, and almost all other classified waters in the
state have a 5.0 mg/L minimum criterion. We therefore see no
appreciable advantages to using the new approach and criteria.
Response; There is evidence (cited in the new criteria
document) that strongly suggests that salraonids and other cold-
or coolwater fish have higher dissolved oxygen requirements than
most warmwater species. However, the amount of data for
nonsalmonid fish is limited. The coldwater/warmwater dichotomy
was not simply the result of some states use of a similar
dichotomy. There are data to support differences in requirements
of some species and the agency framed the criteria to allow those
States wishing to use some type of dichotoraous standard to do so.
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The agency supports the concept of site-specific criteria and
taking local conditions into account in establishing local
standards. But there simply are no data upon which the agency
feels confident enough to establish regional criteria; it is
difficult enough to establish general National criteria on the
entire data base available.
Criteria are intended to be used as guidance in making
resource management and regulatory decisions. Not to use the
criteria is not to read and evaluate their content with respect
to an applicable problem. Why not use the new criteria document?
The new document reviews three-times as many references and
contains nearly ten-times the discussion as the old criterion.
The existing standards described in the comment (6 mg/L
minimum for salmonid other life stages and 5 mg/L minimum for
other species) appear to be reasonably consistent with the
proposed criteria. More detailed discussion of this point can be
found in responses to other comments.
Comment: EPA concludes that nonsalmonid coldwater fish data
supports their similarity to salmonids but discusses data for
smallmouth bass and other species under the salmonidae
[nonsalmonidae?] section of the . report. It is unclear which
species category/ salmonids or salmonids and like species/ are
used to develop the coldwater criteria. The report should be
reorganized into two groups: 1) discussion of data for species
used to develop the coldwater criteria; and 2) discussion of data
for species used to develop the warmwater criteria. Also/ the
critera headings should accurately reflect the type of species
represented; ie./ the coldwater subheading on page 26 should be
"cold and cool water critera.", The nonsalmonids section is
poorly organized compared to the salmonids section (e.g. behavior
responses discussed under growth/ larvae activity discussed under
behavior rather than early life stages). Subheadings under each
section should be similar.
Response; EPA makes no conclusions regarding specific
nonsalmonid species to be included in the coldwater category.
The agency states that some likely candidates may be herrings/
smelts/ pikes/ and sculpins. In another section/ the agency
reports that walleye/ pike/ and smallmouth bass are three species
of nonsalraonid fish that have more-sensitive early life stages
than most other nonsalmonid fish species and that these data tend
to support grouping them into the more-sensitive coldwater fish
category.
In discussion of nonsalmonid growth data the northern pike
is called a nonsalmonid coldwater fish; this was not an attempt
to define the species categorically/ but rather an attempt to
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identifiy the data as from a species representative of those
nonsalmonids often included in the coldwater category.
n
The arrangement of the criteria document sections
Salmonids" and "Nonsalmonids" has been changed to a more
parallel construction.
The question of where to place behavioral observations from
growth studies or early life stage tests must be one of judgement
based upon relative emphasis. Thus/ the behavioral observation
from the Andrew et al. (1973) channel catfish growth test were
included with the discussion of the growth data because the
behavior related to the dissolved oxygen concentration having an
effect on growth. Similarly/ the larval largemouth bass behavior
noted by Spoor (1977) was deemed to be more important as a
behavioral phenomenon than as an effect to be discussed in the
early life stage section. Placing the same observations in two
separate sections is too redundant for such a short report;
placing them in one section instead of another will always seem
an illogical choice to some readers.
Comment: There is no clear rationale for applying the titles
"coldwater criteria" and "warmwater criteria" that are used in
the proposed national criteria (Table 6). Almost all of the
criteria document's general conclusions/ as well as the data used
to form those conclusions/ are .based upon whether a fishery is
salmonid or nonsalmonid. The proposed national criteria should
be categorized as salmonid and nonsalmonid in order for the final
criteria to be consistent with the data that are used to develop
those criteria.
Response; The agency agrees that most coldwater fish data are
from salmonids atnd that no discussion of coldwater species is
carried out per se. The formatting of the text of the criterion
reflects the data availability as well as the fact that there is
no recognized taxonomic standard for a grouping called "coldwater
fish". Many states have seen fit to use the descriptive terms
warmwater and coldwater in their dissolved oxygen standards.
From the agency perspective the proposed coldwater criteria must
be applied to salmonid waters; they may be applied to other
species at the discretion and judgement of the.states or other
recommending agencies.
Comment; The sensitive nonsalmonids should be specifically.
identified by the EPA and evaluated to determine if a separate
criteria applicable to the spring and summer months in which
Ahese species spawn should be applicable.
Response; Criteria for coldwater fish are the recommendations
for all salmonids and any other species (presumably only
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coldwater or coolwater species) deemed to require that degree of
protection. There are limited data on pike and yellow perch that
suggest the former are sensitive/ the latter tolerant of low
dissolved oxygen concentrations. Protecting yellow perch with a
pike criterion might be overzealous; protecting pike with a
yellow perch criterion might be negligence. Both species are
usually identified as coolwater fish. EPA believes that at this
time it is better to allow flexiblility to the states regarding
those species to be placed in the coldwater category; the
decisions are largely dependent upon local data, practice/ and
conditions. Adopting rigid coldwater and warmwater species lists
would destroy the necessary flexibility.
The differences between water column dissolved oxygen
criteria for coldwater and warmwater early life stages are so
small that the necessarily tentative placement of nonsalmonids
into either a coldwater or warmwater category would have little
practical advantage considering the meager basis for such a list.
Comment: We concur with providing separate criteria for
warmwater and coldwater fish and for different life stages.
However/ EPA's statement regarding application of the coldwater
criteria should be revised to include: 1) a definition of
coldwater and coolwater; 2) a statement of the type of
sensitivity common to these species; and 3) a statement
concerning who would make the ultimate determination upon which
any standard would be based.
Response: EPA is pleased with your support for the concept of a
coldwater and warmwater dichotomy as well as the separate life
stage categories. Several other commentors share your concerns
regarding the application of these criteria. The agency will
clarify these points in the text to the extent possible. The
primary point to emphasize is that it is the state that is to
make and support the decision of which/ if any, nonsalmonid to
include in the coldwater category. This is exactly the situation
as it exists currently; some states have standards for salmonids/
some for trout/ some for coldwaters/ and some for warmwaters.
Many of the states use these terras in dichotoraous standards, some
others do not. Additional response to your comments is found in
the response to the comments immediately preceding and following.
Comment: There is no clear definition of what constitutes
coldwater and warmwater species of fish. The document does not
include a definite list and additional information on species to
be considered sensitive. Since nonsalmonids are a large and
diverse group, identification of all sensitive species is highly
unlikely considering the limited data base.
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Response; The low liklihood of identifying all sensitive species
is exactly why the agency provided no species list of sensitive
and insensitive nonsalraonid fish. The purpose of the proposed
approach is to let the decision makers act on local data/
practice/ and conditions in establishing standards or practices
relating to dissolved oxygen reductions.
Comment; We are concerned with the statement that the coldwater
criterion could be applied to waters containing sensitive cool
and warmwater fish (channel catfish/ walleye/ northern pike/ and
sraallmouth bass). This statement is made rather casually when in
fact its implications are tremendous. If the coldwater criterion
is to be applied to water containing these fish/ treatment costs
for facilities discharging to water quality limited nonsalmonid
streams would increase substantially. EPA should expand on this
statement to make their intent more clear. Under what
conditions, if any/ should states apply the coldwater criterion
to protect these cool and warmwater fish? For instance, would
EPA approve advanced treatment funding for a facility to meet the
coldwater criterion if.the discharge is to a nonsalmonid stream.
Response; The statement in question makes no mention of
warmwater fish/ rather/ it states/ "waters containing other cold
or coolwater fish deemed closer to salmonids in sensitivity than
to most warrawater species." States therefore may apply the
coldwater criteria to any waters containing cold- or coolwater
species that are deemed by the state to require that level of
protection. "The decision is probably geographically specific and
is unlikely to be absolutely clear-cut because current data are
sparse. The main point is that coldwater dissolved oxygen
standards currently protect more than salmonids and such
protection may be appropriate for some species.
Comment; It is unclear whether channel catfish/ because of their
purported sensitivity/ should be in the coldwater or warmwater
category. Although ambiguous because of its grouping with
walleye/ etc./ we do not believe that reported data supports
assigning channel catfish to the coldwater category/ and the
intermediate growth sensitivity reported in the document appears
to support our position.
Response; There was no intent to include the channel catfish in
any tentative listing of coldwater species. Data on dissolved
oxygen and early life stages of catfish merely indicate a
tolerance similar to that of several other species that are
considered coolwater species and that may have a sensitivity near
that of salmonids. Channel catfish should be protected by the
warmwater criteria for dissolved oxygen.
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Comment; The document confirms that walleye/ smallmouth bass/'
and northern pike are clearly intended to be classified as
coldwater species. A large number of reservoirs and a few stream
segments in this state support smallmouth bass/ and some
reservoirs contain walleye. Some of the reservoirs may naturally
exceed dissolved oxygen criteria for early life stages/ and
similar problems are encountered in put-and-take trout fisheries
at hypolimnetic releases.
Response; The agency accepts the use of the cited data to
support the inclusion of these species in a coldwater category.
This may be especially relevant in states where the species are
native. In some locations where species have been transplanted
into warmer waters/ maintaining of coldwater criteria values may
be unattainable. That is not to say that the population would
not be better off at higher dissolved oxygen concentrations/ but
failure to attain coldwater criteria concentrations should not be
allowed to constrain nonnative fish management or put-and-take
fisheries.
Comment; The result of widespread early life stage requirements
could be stringent dissolved oxygen standards that may not be
achievable in many streams and lakes. Yet/ in some streams/
spawning of certain species is a marginal activity not critical
to the fishery. At other sites/ where a variety of forage fish
are present with a broad range of jspawning times/ it should not
be necessary, to consider the spawning requirements for each and
every species. The states would face a tremendous burden in
trying to make these kinds of judgements regarding significant
and insignificant consideration for specific streams and basins
without substantially more guidance from the EPA.
Response; The early life stage criteria minima (5 mg/L in gravel
for salmonids and 5 mg/L in water for nonsalmonids) are identical
to the last (Red Book) dissolved oxygen criteria/ criteria that
are matched or exceeded year-around by most states' current
dissolved oxygen standards. Therefore/ the only aspect of the
proposed criteria that might be "more stringent" are the 6.0 and
6.5 mg/L 7-day mean values for warmwater and coldwater fish/
respectively. If daily or weekly dissolved oxygen cycles of 2 or
3 mg/L occur then the mean criteria will be met if the minima are
met. If dissolved oxygen cycles are less than 2 mg/L/ then the
new criteria are indeed more stringent.
The criteria are intended to be protective of most of the
species of aquatic organisms. Selecting species as worthy or
unworthy of protection is not a specific function of national
water quality criteria. Standard setting is the proper arena for
site-specific judgements.
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Comment; The proposal of using a threshold value of 6 rag/L to
calculate an average dissolved oxygen concentration is a good
idea. However; other means of addressing the effect of maximums
on average values should be investigated and include: 1)
utilizing a geometric average versus an arithmetic average; 2)
utilizing dissolved oxygen concentration vs. time area
calculation; or 3) utilizing minimum values only. We prefer
option 3 for a number of reasons. First/ it is the low dissolved
oxygen concentrations that are of concern for protection of
aquatic life: a minimum and average of the minimums should be
considered adequate to protect aquatic life. Second/ utilizing
maximum values to calculate averages does not seem consistent
with past ways of using dissolved oxygen data. It seems in most
cases where extensive data are not available, the 5 mg/L value
has been used as a minimum value based on data taken at various
times and places without consideration of whether the data is a
minimum or maximum value or somewhere in between.
Response: The agency does not support using 6 mg/L as a
threshold value in calculating mean dissolved oxygen
concentrations. We suggest using air-saturation values as an
upper limit. The use of the 6 mg/L no-effect threshold for the
data of Stewart et al. (1967) is critical to several of the
conclusions in the criteria. Namely/ the equation of a mean
dissolved oxygen concentration to a constant one makes possible
the application of data from constant exposure tests to dynamic
natural systems/ and also to the proscription against using
supersaturated oxygen values in calculating daily dissolved
oxygen averages.
The use of a geometric mean dissolved oxygen concentration
actually provided a slightly better fit to the data/ but the
improvement was not sufficient to warrent a further complication
of what are already relatively complex criteria. We have
suggested the use of a time-weighted mean, but would not expect
its use for reasonably sinusoidal or small diel cycles.
The agency does not believe that utilizing only minima says
anything about the dissolved oxygen exposure other that to state
the clear fact that the mean and the maximum are higher than the
minimum. EPA disagrees that only minimum dissolved oxygen
concentrations are of concern. The only way that a minimum alone
is protective is when it is set at a concentration that is also
safe as a constant exposure concentration. EPA believes that
establishing minimums alone as national criteria must result in
either underprotection or overprotection. In some instances
there may be little choice but to use minima alone, but where
-acute and chronic data allow/ especially when augmented by data
von variable exposure/ 2-nuraber criteria are preferable.
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Comment; EPA1s dissolved oxygen document should state that daily
dissolved oxygen fluctuations as a result of BOD or other point
source loadings should not be allowed/ but naturally occurring,
primary production-related fluctuations should be recognized in
modeling the effects of discharges to surface waters.
Furthermore, the document does not reference dissolved oxygen
fluctuation data for coldwater species.
Response: The agency disagrees. Dissolved oxygen cycles are not
known to be inherently adverse. Causing dissolved oxygen cycles,
or more accurately, enhancing or otherwise altering cycles,
cannot be interpreted a_ priori as being an unacceptable
environmental effect. The agency agrees that recognition of diel
cycles will need to be included in models designed to check
compliance with a 2-number criterion.
The document cites two papers that describe effects of daily
dissolved oxygen fluctuations on the growth of salmonids (Fisher,
1963; Whitworth, 1968). We know of no others relating to
coldwater fish.
Comment; Calculation of daily means (Table 7) using "above air
saturation" values is inconsistent with using 6 mg/L as a
threshold. The guidance states that maximum dissolved oxygen
concentrations over 6 mg/L have no beneficial effects on fish
growth, so consideration of maximum dissolved oxygen
concentrations again seems unwarrented.
Response; The data example in Table 7 do not use values over air
saturation: the footnotes indicate that air saturation values are
substituted whenever concentrations above air saturation occur.
The 6 mg/L threshold value cited in the text was for one species
in one study, arid cannot be extrapolated to all species and all
conditions.
Comment; The EPA should withdraw their proposal to establish air
saturation values as the maximum dissolved oxygen concentration
for the purpose of calculating the average daily mean. The EPA
conclusion that higher dissolved oxygen values had no beneficial
effect.on growth is based on very limited information.
Response; The implications of allowing values over air saturaton
to be used in calculating mean dissolved oxygen concentrations
are too important to ignore. There is considerable reason to
believe that very high values for dissolved oxygen would have
little if any beneficial effect for aquatic organisms. Growths
swimming, and blood oxygenation data show little or no
improvement resulting from constant dissolved oxygen
concentrations over saturation. The EPA analysis of the
40
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largemouth bass growth data from Stewart et al. (1967) indicate
that this conclusion is also appropriate for cycling conditions.
Comment; If the daily maxima are reduced to the air saturation
values/ then the effect would be nonsinusoidal daily cycles of
dissolved oxygen that would require a time-weighted average.
Response: The restriction that no values over air saturation can
be used in determining mean daily dissolved oxygen concentrations
would require the use of time weighting. Such computatuion is
simple if sinusoidal patterns are assumed or if continuous
monitoring is performed.
Comment: If supersaturation of dissolved oxygen is noted, other
dissolved gases/ particularly nitrogen, may be present at
sufficient levels to cause gas-bubble disease.
Response: This certainly can be the case where supersaturation
is not the result of photosynthetic activity. Most waters
experiencing total gas supersaturation (e g. below dams) are
dealt with by agencies aware of the problem so that discussion of
supersaturation of total gases is not considered necessary in
this document.
Comment: In most cases the rationale used to develop the
dissolved oxygen criteria presented in the document are well
thought out and expressed. The use of specific numbers for
oxygen criteria that are expressed as average values over
designated time periods is preferable to the use of absolute
numbers or percent saturation values.
Comment: Calculation shown in Table 7 assumes either continuous
dissolved oxygen monitoring or monitoring sufficient to
accurately define minmimum and maximum dissolved oxygen
concentrations. It may be easier to focus only on minimum
values. Monitoring efforts would be less and minimum dissolved
oxygen concentrations would be more representative of impairments
imposed. There needs to be guidance on how to apply criteria
where available data are not extensive.
Response: Determining minimum dissolved oxygen concentrations
requires either continuous monitoring or daily sampling at the
time of mininum daily dissolved oxygen, usually very early in the
jnorning. The number of stations that can be sampled per person
"i,s limited by travel time between stations. If gathering of
minimum dissolved oxygen concentrations is possible, then
measuring maximums would require about twice the number of
samples, but the high values are at least attainable at a more
41
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convenient time of day. The agency doubts that many existing
data bases are limited only to minima/ but contain a broad
spectrum of values. Lack of an extensive data base is
essentially as great a liability for minima as for means.
Comment: The statement regarding nutrient control to protect
against dissolved oxygen impacts should be emphasized as a
possible means of further improving dissolved oxygen conditions
after oxygen demanding materials are controlled to the maximum
extent possible.
Response; The agency will consider expanding on the subject
statement. Perhaps detail on this type of application issue
would be more appropriate in a separate implementation document.
Comment; Naturally-occurring dissolved oxygen concentrations
below 5 or 6 mg/L are common in some situations/ eg. slow-
flowing streams/ high altitudes/ or warm temperatures. The
criteria appear to rely almost exclusively upon laboratory
results rather than natural stream temperature/dissolved oxygen
data/ which would be more meaningful. We suggest that the
criteria should clearly allow the use of ambient dissolved oxygen
concentrations as acceptable where the natural concentration of
dissolved oxygen does not reach the recommended level.
Response: The criteria do provide for circumstances where
natural conditions (such as elevation) preclude attainment of the
criteria; "where natural conditions alone create dissolved
oxygen concentrations less than 110% of the applicable criteria
means/ or minima/ or both/ the minimum acceptable concentration
is 90% of the natural concentration." Thus/ at a natural value
of 6.2 mg/L the ; ^comparable criterion value would be about 5.6
mg/L. A footnote to Table 6 (the criteria) will be added to call
attention to application of the criteria in circumstances where
natural dissolved oxygen concentrations are below the criteria.
Comment; Probably the most important issue concerning naturally
low dissolved oxygen conditions is the statement on page 28 of
the proposed criteria whic allows the instream dissolved oxygen
to be lowered to 90% of the natural concentration of dissolved
oxygen when this value is less than the minimum criteria. The
90% value may be appropriate for natural conditions between the
concentrations of 5.5 and 3 mg/L but should never be used below a
3 mg/L daily average concentration. As you can see from tJ\e
enclosed material we have documented natural conditions less than
the 3 mg/L and feel strongly that 90% of the natural
concentration would have killed the forty native species of fish
found in the Dutch Creek site.
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Response; EPA believes that while it may be appropriate for a
standard to contain statements such as "never allow any reduction
vrtxen.natural concentrations are below 3 mg/L," there is no reason
to insert such a proscription in this criteria document. The
agency will reword the warning about allowing reductions below 3
mg/L to make it more clear that such reductions should be allowed
only if data are gathered on the appropriate populations and such
data indicate that no adverse effect will result.
The agency would point out that other data you supplied
indicate that Boat Gunnel Slash/ with mean and minimum dissolved
oxygen concentrations of 3.2 and 2.7 mg/L/ respectively/ might be
allowed reductions to 2.9 and 2.4 mg/L by the EPA formula. These
dissolved oxygen concentrations are above those reported for
Dutch Creek and which appear to support a community of 40 species
of fish. In any case/ EPA believes that local data and the
evaluation of local biologists are critical to such decisions.
In the absence of significant evidence to the contrary, EPA will
suggest that reductions below 3 mg/L are ill-advised.
Comment; The sentence regarding "Special care...be
taken...before allowing any dissolved oxygen depression in the
potentially lethal area below 3 mg/L" is of concern. First,
dissolved oxygen must not be allowed to approach 3 mg/L where
fishery protection is necessary. Second, potential is not
appropriate as 3 mg/L was identified as lethal. Third, if
discussing natural conditions/ the term "allowed" is not
appropriate. The real question is how EPA~~ recommends using
background conditions in calculating required point source
effluent limits if the background dissolved oxygen concentration
is less than the criteria values.
Response; First/ natural dissolved oxygen concentrations are not
controlled by regula:tory agencies/ they are controlled by natural
conditions and are not "allowed", they simply exist. If natural
concentrations approach 3 mg/L, fishery protection must use that
as a starting point. Second/ while 3 mg/L has been identified as
a concentration below which acute lethality can occur/ such
occurence is species and condition specific. For some species
considerable change in production potential will occur from
reductions below 3 mg/L without incidence of lethality. The
agency believes that fish populations found in waters with
extremly low natural dissolved oxygen concentrations are less apt
to contain species of great sensitivity to low dissolved oxygen
concentrations. Third, the agency will amend the statement so
that it suggests not allowing further reductions where naturally
'^Ipw dissolved oxygen concentrations fall below 3 mg/L; this is
Hot to be confused with "allowing" natural conditions to occur
point one, above).
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Comment; It should be emphasized that the five factors
determining the significance of conditions failing to meet" tire
dissolved oxygen criteria should not be used to "excuse" effluenrt
limits violations or unperraitted discharges. The factors should
be incorporated into application of the dissolved oxygen criteria
to particular cases and in calculating necessary effluent limits,
Response: The agency intends that these factors be used to
evaluate criteria application/ not excuse violations of
standards. However/ these five factors are important in use-
attainability and related analyses and must be considered in the
standard setting process/ in waste-load allocation/ in monitoring
patterns/ and in socio-economic evaluations.
Comment; Stream standards should not be based on "artificial"
augmentation of stream flow by requiring reservoir releases.
Manipulative discharges should not be included for "protection"
of dissolved oxygen concentrations because wasteload allocations
are typically based on low flows or "natural conditions".
Response; The discussion of manipulable discharges was not
intended to imply flow augmentation to protect dissolved oxygen
concentrations impacted by other effluent discharges. Flow
augmentation is a valid management practice for dissolved oxygen
control/ but such matters are beyond the proper scope of the
criteria document. The intent of EPA in discussing manipulable
discharges is to stress that controlled compliance to the letter
of the criteria would be considerably less protective than using
criteria, values as worst-case conditions in a design flow
application. The more stringent minmiroum of 4 mg/L would be
required to achieve a similar degree of protection under
conditions of continuous minimum compliance.
Comment; We are concerned that EPA's discussion of manipulable
and controlled discharges may signal application of s.tringent
criteria to reservoir releases that have not been considered as
discharges of pollutants. They are not regulated under the NPDES
program or water quality based effluent limitations. While we
are pleased to see EPA continue to acknowledge that controls must
be site-specific/ we do not agree that the Clean Water Act or
longstanding EPA policy permit application of numerical ambient
water quality criteria in this way. If any additional controls
are needed/ management practices are the proper approach/ not
numerical effluent limitations.
u
Response; The criteria document offers guidance not just for the
standards setting process but for other uses as well/ including
management plans. The discussion of manipulable discharges 'is
intended to show that strict adherence to the allowable minima
44
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£jesgribed in the document for use in hydrological models with
|l/efin£dr return periods are not as protective if applied as
-continuous attainment targets.
Comment; Many reservoirs are authorized for specific purposes
such as flood control/ navigation/ water supply and hydropower.
The new criteria should be flexible enough to allow for economic
considerations in the selection and implementation of remedial
measures.
Response: The section on manipulable discharges will be clearly
prefaced with a statement that the discussion relates to guidance
only and that mention of reservoir releases does not signal a
change in the agency's policy regarding NPDES applicability to
such releases. However/ there may be some point source
discharges that operate essentially as manipulable discharges in
the sense of this section of the criteria/ and they should be
subject to the more stringent minimum of 4 mg/L.
Comment: Resleases from some dams are periodically well below
..the dissolved oxygen criteria. The dissolved oxygen sag develops
gradually and fish move downstream to avoid the problem. No fish
'kills have been observed due to this temporary condition and
'reservoir operation to solve the problem may do more harm because
.of supersaturation with nitrogen and other gases. Therefore/
.case-by-case judgement needs to be applied to releases below dams
'with regard to any application of these criteria.
Response; Avoidance by fish of harmful dissolved oxygen
concentrations can minimize the impact of low concentrations/ but
^is not entirely without potential adverse impact itself. Among
the effects are increased vulnerability to predation, disruption
of feeding/ stress due to territorial behavior/ and disruption- of
spawning. Embryos and larvae may not be able to avoid the low
dissolved oxygen concentrations. Periodic releases of low
dissolved oxygen water from dams is not inocuous.
You are correct that how individual projects balance the
environmental (and other) impacts of operation alternatives does
indeed require case-by-case judgement. The agency believes that
the new dissolved oxygen criteria provide more basis for those
judgements than the old criteria.
Comment; The discussion regarding manipulable discharges is
unclear and confusing. It should be rewritten so that the
^-technical basis for these criteria are more clearly explained and
^,','^he ' application period and the applicability downstream are
':. Velar if ied.
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Response; It is clear that the intent of this section has not
been adequately expressed. The section will be rewritten. ^
• ' . '->.*"' /)
Comment; EPA's proposed need for and/or establishment of the 30-
day mean criteria is expressed. Not only is the value of the 30-
day mean not justified in the criteria/ but it would also place a
constraint upon the operations at American Falls power plant and
possibly many other sites/ that is virtually impossible to work
within. At present when dissolved oxygen concentrations at
American Falls decrease to 6 mg/L/ power plant operators start
aeration devices to lessen any impact of the uncontrolled
dissolved oxygen concentrations within the reservoir. If
dissolved oxygen continues to fall and reaches 5 mg/L/ a spill
program is implemented to maintain that level or above. This is
a scenario within which operators can work. Operation
constraints that require a crystal ball for looking 30 days in'to
future are not reasonable.
Response: The 30-day mean was selected as a familiar reporting
period and as a period over which growth effects might,be
meaningful. The specifics of the criteria are guidance0fbr
regulatory agencies to use in developing standards or to evaluate
management practices. As to their application to specific sites
or operations one can only speculate/ however/ data from .the sivte
mentioned indicate more problem with maintaining the simple^ 5
mg/L minimum than either of the proposed EPA minima. Curr.ent
practices appear to meet the proposed criteria better than they
meet the existing operational goals.
Comment; The mid and late life stage dissolved oxygen criteria
termed "Other Life Stages" is quite compatible with the old I9t76
guidance and most existing state water quality standards. T-he
new recommendations for a tiered approach providing "Early Life
Stage" criteria is also reasonably defended although many states
would need to revise their water quality standards to accommodate
the' new guidance. Selection of 30/ 7/ and 1 day criterion values
"• is; very welcome since it allows computations to be applied
consistent with current permit averaging periods.
Comment; Because of the complexity of the proposed criteria .EPA
should establish a two-tiered approach. First/ the current "Red
Book" approach to establishing a minimum concentration of
dissolved oxygen should be retained as the basis for criteria
that would be generally applicable nationally. Second/ :EPA
should develop scientifically sound guidance for applying
more flexible criteria on a site-specific basis.
Response; The basis for the updating of the dissolved oxygen
criteria has been explained. Whether parallel changes in
46
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s'tandardg~will follow depends on the evaluation of many factors/
the most"important of which is comparison of current standards
and these new criteria. In many instances/ current conditions or
existing standards will meet or exceed the new criteria.
'Comment; "The flexibility which will be brought about by the 30-
''clay mean/ 7-day mean/ and 1-day minimum will make the
BOD-dissolved oxygen water quality monitoring game much more
'^'complex.; It; will also require more intensive field studies in
order to evaluate compliance of specific dischargers. In
' addition/" this type of criteria could antiquate ambient
;monitoring data and at a minimum would call for new and
L_ innovative ideas in evaluating monitoring data. We are not
' saying that these are negative points/ only that an early
^understanding of these issues will help in pursuit of the goals
°of the Act.
Response: The agency is very much aware of these complexities/
;'especially the modelling and monitoring connotations. The same
"•'problem exists for all the new toxic chemical criteria. In
"providing flexibility we introduce complexity. The . agency
-•believes that waters currently meeting the 5 mg/L minimum
fcriterion will frequently meet the new criteria. This situation
J"vi-ll follow from the existence of diel dissolved oxygen cycles
; that will cause the mean concentration to be considerably higher
than the minimum/ and the effect of annual cycles of dissolved
:'bxyg>en resulting in higher dissolved oxygen concentrations, during
spawning of at least some species.
•'- Comment: If one has a dissolved oxygen standard that varies with
•" season/ daily, weekly/ and monthly means/ as well as: p6teri¥Tal
Ispecies difference's/ it appears enforcement would,; become
-•impractical.. ,,,;•.,
-£* a " -:
Response;- Standards that meet the intent of the criteria may not
- need to be as complex as the criteria themselves. Continuous
"•monitoring may be required in some cases to document compliance
or noncompliance. Current monitoring practices which presumably
are for the checking of daily minima often in fact do not record
such. It is difficult to accurately measure daily minimum
" ^dissolved oxygen concentration without continuous monitoring.
w,, i~
." c
^ iComment; We commend EPA for its efforts to achieve more flexible
A dissolved oxygen criteria. EPA1s efforts to derive dissolved
srttxygen criteria that vary according to fishery needs, life stage
needs and length of exposure are justified by the available data.
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Comment; Several inherent problems would have to be addressed"£1
theproposed criteria were used in revising water quality
standards. The time period for the application of different
criteria for different life stages would need to be specified by
some method - perhaps by date.or water temperature. It would be
necessary to determine which criteria would apply to specific
water bodies and when different life stages were present. This
would require sampling to determine species present and
researching the literature to determine spawning requirements of
the species present. We reiterate/ however/ that in this state
there are early life stages of different species present from
early spring to late fall necessitating the application of the
early life stages criteria most of the year.
Response; Some of the knowledge required for application of th$
new criteria format to standards will be available in. the surv;ey
reports of state fishery biologists. States that currently have
trout/ salmonid, or coldwater standards have already faced thte
classification of their waters. Those states lacking these
special classifications often have other types of classifications
based on local requirements or use-attainability. Many of these
standards are sufficiently stringent to protect . all species/ or
the states know that they do not have salmonids or sensitive
coolwater. fishes. ....-.'. ~?~
.Determining when early life stages are present will' usually
place additional responsibility on states wishing to make 'such
evaluations. Application of early life stage criteria year-
around will be applicable in situations where such data are
lacking or early life stages occur year-around. Warmwater early
lifje' stage criteria are often complied with where standards
specify a 5 mg/L minimum. "
Cpmment; Our present ambient monitoring program includes only
one sample per month/ so only the one-day minimum could be easily
ap,p.lied. The other criteria appear to have a reasonable
^biological rationale/ but it would be very impractical/ if not
impossible/ to try to enforce standards derived from these
criteria unle:ss a more intensive sampling program were initiated
or automatic sampling equipment used.
Response; If minima can be adequately monitored by measuring
dissolved oxygen one day in thirty this implies some predictive
capability towards the missing 29 days per month and presumes
reasonable timing of the sampling with respect to diel cycteaj.
The same predictive capability can be used to at least esti'ma^tfe
monthly and weekly means. Occasional estimates of diel pulseris
would probably be required. States using daily average"dissolved
oxygen concentrations in their standards should also have 'sp'me
idea of daily minima and diel cycles/ or they are ignoring' th'e
48
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potential:, _ impact of daily minimum dissolved oxygen
concentrations.
Comment: .We have been involved for the past 10 years or more in
implementing a 5 mg/L dissolved oxygen criteria [standard?] for
?ifish and^ aquatic life" waters through a wasteload allocation
program. . !T In the most prominent cases we have employed complex
computer'models and sophisticated allocation techniques to assure
water quality is adequately protected/ but still allow continued
operation", of the sources of BOD to these rivers. Even with these
models which we believe are "state of the art"/ we are not able
to determine if or how we would be able to meet the recommended
criteria. We cannot imagine how the criteria would be
Implemented for situations with less complex models or analyses.
The,point! of this is we believe EPA has created a criteria which
is so complicated that those who must implement the criteria will
be unable to"..do so in a reasonable fashion. As such/ we predict
analysts will become discouraged and permits/ rather than being
Issued to meet the water quality criteria/ will revert to the
categorical technological based limits. We are concerned this
.complicated criteria is little better than no criteria at all.
Response: You currently have different standards for different
bodies of water based on species present/ use-attainability/ or
water,, temperature. You currently use a diel cycle factor in your
.dissolved oxygen modeling. Except for knowledge of when early
life "stages .are present these are the only items needed to
^implement, standards that are formatted in the same manner as the
proposed criteria. With reasonable documentation "of ' daily
dissolved oxygen cycles and annual patterns/ perhaps augmented^by
spawning times/ a single minimum dissolved oxygen standard., could
be shown to be compatible with the new criteria. " " &s'
Comment: Additional comments must be made on the diffic-ulty--of
working with such a complicated proposal. It is not clear i\pr
any situation whether 5.5 [30-day] mean/ 4.0 seven-day {ite^m
minimum/ or 3.0 one-day minimum are equivalent. If not/"; which^is
,more limiting and how do you determine it? Clearly/ ' the iikefly
distribution of dissolved oxygen values must be evaluated from
the standpoint of algae diel effects and expected discharge
^distribution effects. In either case/ evaluation of the proposal
j.s riot simple/ and perhaps an impossible task.
f* ^. •" i *
ttes'pon'se: It is apparent to the agency that the controlling
^fac.tor will be either the mean or the mean minimum (other life
^tages) or minimum (early life stages). The deciding factor will
ib^e the magnitude of the diel cycle. The one-day or instantaneous
jijlrii'mum. for other life stages is only a floor for allowing
J. Infrequent/ nonlethal drops in dissolved oxygen. Failure to
"account'for algal diel effects is a severe short-coming with any
49
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dissolved oxygen standard/ for such failure can ? res,u;ltr j^n
significant under- or overprotection. . . ,c -.-,--,
••• '. i-e~- el
Comment; We believe that one of the major proposal -impacts^will
be in the modeling and waste load evaluation program.. At..the
present time/ we utilize steady-state dissolved oxygen-models/
with calibrations and projections based on mean dissolved oxygen
over a 24-hour period. Adoption of the new .criteria;wi11
necessitate using a time-variable model or an empirical .-site-
specific determination of dissolved oxygen flux and .a .method :,to
predict diurnal flux under altered waste loads.' Further,- the
methodology used to select critical conditions will need- to ..be
revised to consider protection of early life stages. .'Also/.more
extensive diurnal data will be needed to calibrate,models;
nutrient and photosynthetic interactions will: need:-to be
considered to quantify diurnal fluctuations, and a .method'for
quantifying macrophytes may also be needed, . Finally/ the
evaluation of alternatives will be substantially more - complicated
if all five mean and minimum categories [for warmwater fish] are
to be simultaneously considered because various time periods•„will.
need to be analyzed/ and corresponding permit limitations (ot'ber
than just a 30-day average) will have to be evaluated; ^ While
presently unquantifiable, the cost of revising the state-s
dissolved oxygen modeling program is expected to be'Substantial;
''•"''- _ • j. "-""• ".*•.••':
Response; The dissolved oxygen standards for waters in your
state are minimum values (usually 5 mg/L) except that - for-short
peri'o~ds of time diurnal variations of 1 mg/L below these-"mini ma
can - be' allowed for not more that 8 hours during any 24-hour
period. These standards apply at all times the daily flow equals
or exceeds the specified flow criteria. A dissolved oxygen model
that takes into account: 1) an instantaneous minimum of 4 mg/L;
and 2) a time and dissolved oxygen relationship model suitable to
dVfine -the daily period above and below 5 rag/L would reason'atjiy
b'e; expected to handle most if not all aspects of the proposed hew
dissolved oxygen criteria. Now clearly the steady state model
"y^>u- describe -does not enable you to comply strictly to.the sta£e
standards (and this is not an unusual situation nationwide); The
fact that the proposed new criteria are more complex than can be
easily handled 'by your existing models should not/ in itself/—be
taken to "mean that the criteria are incorrect or any more
impractical than existing state standards. Also/ in waiters just
meeting the 5 mg/L daily mean you describe, the die! cycle must
be less than 2 mg/L or you are dropping below the state standard
of 4 mg/L. Therefore/ either you know something about tfie:scale
of the diel cycles/ or you are ignoring the 4 mg/L minimum. ':
' . ... ' <<;'.
o •._; r jo
Comment; Imposition of the proposed multiple criteria approach
would necessitate a tremendous increase in agency mOnitori'rtg
because the new guidelines imply that daily/ diurnal sampling
50
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nwi if -^b:£e" required to determine attainment. At the present time/
the approximately 500 fixed trend monitoring stations in this
state are generally sampled monthly. If daily/ diurnal sampling
is really necessary/ continuous automatic monitors will be
^Fe'quiredSJTat a large number of fixed station locations where
-dissolved-dxygen may reasonably be expected to constitute a
problem ,'3!:. Initial capital equipment costs alone are expected to
'reach one-quarter of a million dollars. Also/ more personnel
'will ; be sree"; no
£.e.xeeptiQrvr to this policy. What is apparent is that rthe? -new
70riteria;,will- :require the states to pay greater attention., to ,-the
£magfiitude : of>j ,.diel -cycles of dissolved, oxygen and the:, -minima^ that
as £he, result of these cycles. .•:.---•-. : c. ; •-, -,c
• • , •, -...• .. . -... . .- :
Comment: The proposed criteria will throw the. burden, uppn? ^tjite
,stat:es .whor frequently have limited resources '-available., -to., do' -"the
_seientif ic evaluation to determine whether the my^riad^ af. .spe,c,tes
c-.that .might be present in different waters .have sensi'tivitj,^
esimilar; to,; salmon ids. '. .. . ...,'. -^ ... ,.:, .. >,-;6-£
.^Response ' . The agency, believes . that ; the ". present . state of
^.knowledge regarding the dissolved . oxygen ' ^e'risitivi ty of
"ponsalmonid fish .suggests a continuum of sensiti vity'ranging from
..very insensitive to salmonid-like sensitivi.ty (and perhaps
j.beyond) j Specifying sensitivity of ..each .nonsalmonid species is
si}ot, possible in any realistic manner. The agency has pointed out
those sp.ecieg that appear to be the most sensitive of the
nonsalmonids, and has suggested other possibly sensitive families
of fish. At the present time it is up to the states to decide
^wh^ether to. place nonsalmonid species in warmwater or coldwater
'Cca1;egories.. Several states simply do this by water temperature.
pr 1 i q7. or. . £
51
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i'-~ ' : •'<".; _;;jpe:r I.', iv
.'."ic• - - 5. bt-o / n i
Comment: The states must develop a monitoring prog-ram-fcRSt
determines compliance of each water body with . the appropriate
average (30-day mean/ the average of minimum results f-or-7 dai^s
or the 7-day mean). This is a laborious program ' 'tRafe-will
severly tax the resources of many states. Expensive J'daea
collection would be needed to measure 30-day averages and even-17-
day averages.
Response i The agency agrees that the most dif f icult •-aspee-ti of
any complex criteria or standard that requires averages""is~tne
problem of compliance monitoring. For this reasonJa;-more simpie
bottom line may be required in standards. The inclusion eofLtfte
concepts contained in the ^new criteria (as ""opposed- to the
format T7 could follow the following line of reasoning:-first? the
decision of if and when to apply early life stagejand':6ther'j'l'i?e
stage criteria would have to be made (the earlyclife ~sta§e cb&ld
be selected year-around as a default position)'"; - second) the
annual dissolved oxygen profile would need to -be;ascertain-ed
(this is presumably already being done); third/ an estimate-of
the diel cycle would be 'needed at least for the' critical-period
of the year; and fourth/ this information would be used to
determine, .„ .the " limiting" minimum concentration - ;or t ••'. '. ') : . - • _ .. .•..•••- o J f - • "S
'feesponset'". Tthe^ ag&h'cy' believes that the critical minimum value' in
the criteria 'will be the 7-day values (either the 7^83 y' mean
minimum for'^ pt,her. life stages or the 7-day means for-' - ea-riy"li?fe
stages). .'.The 3. mg/L minimum is the agency vs attempt ' to InjeVtT a
more realiVtic ' cb^ribept of the lethal cohcentrat'i'on,0 a
concentration not included or discussed in most other dissolved
oxygen criteria. The response immediately above summarizes a
conceptual approach for realistic compliance monitoring-.;. V'r"c
- '-
Comment: Another concern is the application of the- p
criterion in the waste load allocation process. This is- '-h-crt'-'so
much a concern as simply a recognition that the new criterion
52
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will require some changes in the way mathematical models are used
in load allocations. The section on monitoring and design
jgendi!tiojn!s_- in •• the document should help states implement the
eer.jteripn.3 .We appreciate the fact that the 30-day mean criterion
2for other ;.life stages meshes with the 30-day mean BOD5 effluent
rjimitat^on^in NPDES permits. Similarly the 7-day mean minimum
^ciriterioft .-.f or other life stages meshes with our 7-day mean low
flow ,47Qlp)^requirement in our water quality rule.
Our most critical low-flow months for load allocations are
-ikypicallyjiate > summer/ early fall and winter. Since most young-
eP|-the-y§ar-.Karmwater. f ish will be past the sensitive early life
satage by0latersummer/ the less stringent criterion for other life
.^stages should^be the appropriate,target for modeling during these
£eriticalilraon,ths. We feel confident that meeting the other life
.3 stages -:criterion during the critical months will assure
seompliancer-wittyj-Jthe early life stages criterion during the higher
-flow months of spring.and early iummer when this more stringent
eGriteripnris , applicable. We will, conduct the necessary studies
V£r
z cotnsjL^dejrabiy' : •__ ^higher x dissolved ..oxygen cpncentrati6nsr "du^Tng
np^eriods pf j the yedr when early" life stages are present., *'"" '.'^.f?
.' . i • •- • • -.- ..._ .. . .. . , _ ^ •.,,., r ._.
Comment: The proposed ambient water quality criteria ;"
dissolved oxygen represent a great improvement over the exl's'ti'ng
,- crirteria,, ,;f j ,Howeye.r . there are several^. ar,ea^r . in,., the proposed
,cjr,iterri.a- jthaL, , heed to. be addressed" i|i. grpaters"detai-S^-; --Thlse
-areas: include.: ,1,.) .Locations for monitor.i^ig, ; "dl^sp.lved" oxygen and
£ temperature-;,. ,£) \ methods of. deterrainih^VSne,5in"d:ishelved oxygen
s co,ncen-tr-a^ipn; 3) methods of measuring diswso.5Lved. , pkygen; and 4)
j; jappli^a-tio.n of -criteria. ,_ , ''."."•
j-j ;* t. ~^ ^ •*? ,-.. •"'•'•£ i •
Response;.,, -..Four respohdants asked that EPA provide technical
guidance ' on various aspects of dissolved oxygen monitoring
including measurement methods and location and frequency of
5.^i-mp-L\ng_.r;. In general/ the agency sees no reason for changes in
,.^urgent - practices regarding methods and location of sampling.
:-oi -3^^ i-sc, •• ••*•; -.-.
53
-------
-.:- -'A-. .T-eV. -OH.SX.V/
• ' r.': r.ci;.-fr-roD-r
The frequency of sampling will depend upon the extent to which
revised standards mirror the format of the proposed criteria.^3,1$
some instances this would require continuous monitojrongl. ~^t
carried to the extreme. As should be apparent in - re,spp£is,es ztp
previous comments the intent of the new criteria- rma|^ be
implemented v-ia more simple standards if data are c a^aj.lajb.le^.or
gathered to. .confirm the effect of daily and annual- dissolved
oxygen cycles. ._.
Comment; We do not believe, that sufficient data on -= the r^giona-l
response of certain species exist to justify national appljrs^^ripjt
of the early life stage and other life stage criteria. . ,: \ -<.,0
Response: The commentor presumably means that it isl likely tha£
the response of certain species will be different 'In di.ffere.nt
regions of the nation/ and that unless the .. agency^ . kn.o,ws this
response to be geographically uniform no nat-io.naJL" applj.x:a,t4on
should bV.-ma.de.. The age.ncy realizes that regional :di,f fere.nc'e^s
may exist due to environmental or taxonomic variables/" but jr unt.ll
such variables, are identified ,a.nd .their ef f ects. ,qua,ntif igd~ only
general ^a,lue_s are available to be, included in natipKa.!.' cri',ter.;j.a".
Where regional" difference^. ". can be validated! they" " JPJMX trigge'r
site-specific modifications/ but if such ,di,ff e^ences- . ,do; Tipjt
exist/ are minor/ or are only speculative/ a h'ati'o'hai criterion
bas.e_d, upp,n existing data should be the basis for decisions... _ . ,a .
. :>i r '. ~ 69 ./. i: - - •: -. , -; - " j, -.; ' '^c J3'3cc£ I
£ :. " ^ -H,e -Haye _, reservations about the Adequacy Vo'f ft he ~ da't.a
Ause^<3 :tp~ support^ the criteria. We, ; rjecognrize tha"t"; ^ EPA" hi^
i^nue^d ' t'to ' w.ork to develop and " "improve'1 ", '"ijtfc 'jre'
^qapa.b^i 1 i tfie's /7 but would urge that such a_c tivjL^tiVs" ^ ^^e^ B
^* ^enco'uraged. " Too ^ often the number's aVailjibl.e' 'JtV
l"" are used in a fashion" inaVp^o'P^ia^'^^
' We would urge the agency ~tO ; cpnductn;mj>%e
more specie=s of wrarmwater fish/ yilih
Otfh "those in the ^Southern United State's"/, "as
Velcfeivi'ng" wkteifs ar% most likely to be affected by: ttie"
oxygen criteria. Further/ we concur there is a considerable Weed
for more studies comparing laboratory results with receiving
water studies.
•-• -> ST ,".'••"..-- ' ' . • • "-.rt ; :_£ • ,v:v..-".
Response: : "The" ^dequa'cy "of the current data base is questionied/
and it is l^fkel'y !.thatf~the. adequacy of th"e data ba'se" jwrlT:^a-lw¥ys
be questionable. ''Certainly the data available aire Jae;t te^;t±ia|i
those available at any previous time/ and specifically are "mp'rja
encompassing than those available when previous national criteirra
for dissolved oxygen were prepared. •
Comment: We feel that an efficient method of ev'alua-tinrg1"'
-------
dissolved oxygen conditions should and could be based on the
"ecoregion concept" being proposed by EPA's Corvallis laboratory.
fiD.::r!v ;>j ~n. :
Respoftse•:- •' T he agency agrees that geographic factors such as
those11 currently being used in ecoregion analysis may have utility
an 8 Se'para't i ng the environmental requirements £6r biota at
different1' sites based on interacting factors that'-^lnfluence the
tbpnrp&sltlbn6 of' the biotic community. This approach is still
fe^pe'rUmental17and no mechanism or validation for such an approach
is currently available.
ebm'meft't"; ^The 'pressed dissolved oxygen criteria document has a
paucity °x>f l 'information on -the ecological consequences of
behavioral/-repr-oductive/ survival -and growth impacts of various
dissolved oxygen, concentrations on fish. The brief statements on
page yiB" tha'V a'ddress feeding-sTze relationships and predator
avoidance capabTlities are the only 'statements :of this type in
^the; dofeu^ient. ''e ' Yet/ the ecological ramifications :of growth/
sxirviyaljr ^ reproductive and behavioral changes are profound.
1leceWtyisVue;s of all -major ecologidal journals address these
phenomena/"c and" should be consulted'"'and cited in'the document.
Seriojifs^ consideration of ecological "impacts as'srociaited with
gr^wth"/'rsurvryal;> behavioral and reproductive changjes 'roa^y/suggest
t'ha'V: warter Nqua'lity standards be morV stringerff'ttrf^11 those
,~-o.~ -.-•', ,=,'..„•.''15.7? ~ -,r . • . • •' ••• •••• \ -•;- T,- oi '. •~r-'"'&- • '
proposed in the document. . . . . ^^... ., ..c
n•'..,' j S" ' •"•':;. it.-,.: ; "< fi r -. > • •- •-. .- .. • :, 6 . i-
Response';" J t'Ke ^agency is aware that the effects mVa&ur"ed in
laboratory studies are not the only ones that can appear in more
complex natural ecosystems. The agency is not aware of evidence
<=. - c - ' • • • f.. - - - 1- a * >- • y •* . • - • • . ,,• • ! r' c~ rp ff
.that ,in<3legates "that c.rrteria based on common labqratdr-y--%est
^e'n d points "result , Tn significantly less prptectiv^e; ..cr'iteJrTa f€Ha;n
,k>i6jS
-------
the superiority of the algal diet. The criteria are-b^fsed i:bn
fish growth studies and not studies of daphnids. '- Ex-traddla't'iPon
of the daphnid results to fish is certainly nafc'0i?£»soi$iato'Iie.
Prepared fish rations are designed to be nutritionally adequate
for fish, and their possible inadequacy for cladoon Below
natural fc5hcentrations should be tolerable. : :': •' '•-"•"- '-J't~>- -!t ;
^Dis'cdsrsfori of manigulible "discharges like ^reservoir -releases
is in te rio^e1^ 'to provide1 "guidance in cases v?hi>re0condrei6ftsneiari"fbe
maintained at statutory limits for re'iativel?y fll6h'gc pe'fiods "of
time. This guidance could be used in evaluating management
plans,^ release schedules, etc., _but does not imply an NPDES
pofltfy ^change with 'respect to reservoirs. ": : - VD '• : ±£.!:J!^ i
j.. i / 'f • . c ';^ ' ' :. '. c--- :' . " . •- „ * nr ; \i £ '• -. , 2 .;. rs ;. '?•.•• ^ T ,; ;p . •.
; - , ' » n . •• ~. • • ••• :: . '.rc . f >.• ' O':.o
" " ' "Several fr surface waters niay 'hive -both- wSrmwafier' iftd
'coTdwaTer "species f at' "certain times of- the year ^ 'o:: For ^exafnpl^,
several of the rivers in the Great Lake's :area"may have1 salmon"! 9s
pr.esent from late; an the summer to the late spring from spawning
"r'Qns* of'steelhe.ad trout/ rainbow trout/ brown' trbfi't, A co hBH Saitjin.6n ,
a'nd^^chinoolc salmon. Can rthese rivers -be coniidereS both
^seasonally warmwater;-and:coldwater? ; : -••&-•" ; ^•.---''-Icsc s- v^ej-vfcr
or -.-.-.• W':it' • :e fc.. •;•• r r .-.;•- - -1 •••• -. .--;,," . .:;'oL' . t"t. s-2'^c
"fi4sponai4 ;.'^ • °-6n'e intent :- ''of •''the "prdpp^ed criteria isr"'tb
sucn f leiibi;li€;yl ":Itc-is consistent' ';w£t'h' this0 gpal'"1tp ^rottect
only forf the^fiibst^ sensitive use present 'at kny gi verP'tifne! rn"*s";r
• £•:.: :: i t. '* ~> . ? ; :.' " .-: •-.*:. . :'-•-. ± A . ^ ;•;«•• .' ^o .. :^ i .'.
, L-.^,; ;,r q vt d ' ' • .• • . -•• -,;.*:'•:.-:;..• n^, x .n-.z ., .to 06
Comment; Before standards are applied to a water body, the need
for a Use Attainability Analysis should be carefully evaluated
for each case. .; 'The proposed criteria assumes tfiat dislfi-l.vied
oxygen is the limiting factor in protecting "fish. ; ConsiderSt'ibn
must be given to an area's ability to maintain a residertth!i:i]sh
population. Site specific field investigations' 9rarer bf'ten
necessary to determine the fishery potential of an area. The
proposed criteria should require that the Use Attainability
Analysis quantify the magnitude of the influence of background
56
-------
conditions on dissolved oxygen. In the past/ oversimplification
Le,ad sfcp applying a 5 mg/L standard to all places in a water
: -Tali times. The new criteria must be written .in a manner
c discourages (if not prohibits) similar oversimplification.
yllsr..:> . i ri? ! '•
^gS^ch analyses are currently r equi red,. ^in reviewing
standards on water quality limited sites/ and provide .for removal
of a designated use/ adoption of use subcategories/ seasonal
uses/ or similar modifications. These requirements are
r; summarized .in EPA ' s 1.9.83 Water .Quality Standards Handbook.
xErjifr/ wo led ix -••••.• • •-.•••
eci o.ii. orlL eJs,\ . t. • f - ' :v. ." - '-. •••• - ••
-tgommQafc?.' EJtA shjQuld .., encourage further work in ... developing data
pnee^ded.- to ..^determine relationships, between diel and seasonal
if.luctua.tionf ;fO: dissolved ;; oxygeij and fish . ..production and
ecological integrity. ~, ." "
gRespoose;. , EPA .does. encourage .more research on the effects of low
~di s 99 l,ved oxygen \pn aquatic r "or g an4i,s,ras . . The agency .".itself is
rigu^entiy%fynding both marine,, and f'res^water r.esear.c.ti programs to
;:ii7\|^stigate :sth.e !?e,f fects of low ,\>. ^7^j ^ c - - -r £. -. f^ -Jb-;. mc^a -':^:j^^
m§rine, . dissolved- oxyge.n , . criterion^is , planned^, ^.
"
note,^benforthcoming in the hear future,,
review applicable standards in, the. ...light ,of ^t ,v/
-------
>,OOa £ S%
Response; For states that have existing
estuarine -dissolved oxygen standards, the new crit^ria^.w< ^_
application^_;to.-.. . the freshwaters. . The freshgat^r "'crit|i*|a
discussed .-in the. -document are not meant to sugejrcede existing
marine criteria, although the topic of dieln "cyc|fs^shSQld
certainly be a consideration where such cycles can occur. in ;tKe
absence of a definition of freshwater and brackish water, a
possible -mechanism would be to apply freshwate-r criteria to. tho^e
waters wi£h communities that are not predom;ina^£iy_CQmfje-9^^=>f
marine orxestuarine organisms. ., . . "~~77^7,Jj' "',V".,t~R-'r
Comment: The document points f>utr the irapojrta^t^~.rej:fect^ tha't/E'i'sh
life stage .has 'on the sensitivity" o_f fish to ^l.pw \d~JLssoiy 4d'bxygen
concentrations. Because of tjii,s~ and ,the.;.jposj3^iple' ' cpnf'u'd'ion ith^t
will result from the current 'use, of many difcfer.eiit^: y^rt; nearly
" ''
c
synonomp.us, terms for various , periods of, i "f ijsfh deVelopm'entT'ye
suggest ; Otha,t-, ; - t.he . docu^tne.n't , 4\proyide , ' retrfse ! s'tan'dar3\z^d
" "
definit%ofts -for ,.terms ;,suc"h eas" ^l.a"rval,^"r eMbrybni'c,
juvenile./, pearly life stag"e vis' other life stage,' and ocbher_sf:_ i;We
recommend .tjriose terms di^cu^sed %nd refere"'rtcfed _''in^ "Cp'rrbiribuli'i'bns
to a Guide to the Cypflniform Fish Larvae; ;bff"'j'th'e" 'Upper ^plbrlkdo
River System in Colorado" (by Barrel E. ''STftydeTrV* ^Coiora'ofb^S-tfaTte
University, for the U.S. Bureau of Land Management, No. 3
Bio^og^cal ^Sciences S.eries, .19.8,1 / Denver ,^Cplp. K ^^
. Response ; ~ .The agency * i^'aware that nomen'cratui?e6p of ^eaifly^ l-i?fe
- stages c.rfo,f 7fis.hes _.'"is ^confusing (and corf'trov^ers^ar)^ - ?tp'- the
• - gas ^partj.^ f or this . reason f that the eatfiy'-lifei c stage' 1cri'te:tf'ia:'-are
,^j3]gi|ed^pt lpy..,stag^rT3ut by'/time "post-hatc;h:"i: The! ^agency ^be^ieves
that'the time from spawning to 30-daiys'post-hatch erfcompas4e:srctShe
most sensitive stages in general and is consistent -with-the
^xdu^ation, ,,of ,.sta.n,dard early life stage tpxicity^ tests. In
'I'..§^i'tionV.. wse""",ot'••'"7Ja""'.' time 'period avoids ?^po€erit:ially4!?Qt1tfM^ikig
',.. tgrnitinoipgy disagreements or the endbfse merit of £a'n'y 'bite ^ysW-ra "of
'hbrnenclature^ "' "' ~ """ ' .". " ~ ' " c' " J '"'3 ~ i-"-- ''i:1 '• 'n"• "*"• -'•"•'
•• ^ '- •"'• Ov r- j ~r>~ ' i ;•• 1' .'.•:.. nc/w cc-^v.. ' '. .;•>
Comment: "... ' _,pnf" * issiie^ concerning implementati'on "cthat ?^was not
mentipnec^ifiydiyes thir'r6gulatbry impadts^' caused *by aVio^tidn-?of
new, more" s%tingeht^ criteria . In" many^dales/ 'P(5TWr;c
-------
Red Book 5 rag/L criterion is achieved on a 7Q10 basis, the new
riteria will be achieved with regularity. Whenever the daily
it'^6ui1: minimum meets or exceeds 5 rag/lAv 'especially when
i'-sire large (greater than 2 mg/L) it?liPldfcely that all
w efi€itia will be met. Unless the- a qua-tic^cre source at
i isBiSially critical'] no changes in de'sigW s*buld even be
gris!dei?ta~'in raofst instances7:- ^ • .--asi-i- •
? n* .. IUSDO rs.-; . -„• re .-. . - • .--•. : - =... f .- •
O:. S . EPA is' "to be commended r£br^produc ing an
cr Iter'ibn document ~- a.' task made considerably more
difficult because the standard methodology'- r -uded' to determine
criteria for toxic pollutants is not applicable to the dissolved
, oxygen dajta base.. The document is the most comprehensive summary
' s^nce Dobdor'ojf Vnd : Shumway -f!970) and, more
,
ifepbrt^ntly /r i't gpks. be'yond a simple summary of : the- 'literature in
ma ny . r e|pe c.ts^ " t :Vp^r: ': >xamp 1 e r ;t;n¥ f i sh g row t h =• da t a " has been
' " Walyz^e'd sd ;tfhat -"iMr ;is 'more amenable1 -to criteria
.SA'r. in'; deyel;oping S4:he critetfi'oirtr cdn-aideration
^eX ;'to; the"' imp^licatio'nji : "of extrapolatri'rfg laboratory
ed" ^^ider controlled ""conditions , -°€p z&fte natural
., , 'We'^e.l that^th^ ^tuarl-^riter ion jiiuT^er-^ selected
; the, TstcCt.ed 'averaging pe;ri6ds''airfd levels df C'rpfr6£ection as
. *.•« .^j O i;- i '•• t < : t:- • - ' •' c -\ *r""« •' "i r~ T "i ^ : -' • -. - *- *{ e, ? r ' '• ""
- -""
- :^ -. -.-•• -.i/s-f -snt ^ orBJ -: ./^r:;? , ? . U ~- -r "i ,v3Ul'ev.-.
Comment; The riatVohai' 4 criterion "propdsed by the EPAcn*ail>criieatly
gaj>,, .between meager data, admittedly _ fraught with
"' " c
agency'* ^conviction ^ tha£ *±a£L2fii4iier
-, Tstanx^.pd-c mu^s't ,Jb'4 ^^%ined, and ); fan !. esoteric "qualrtCa^fve
s^rqtectjion/risk"^as^W^s^en,t»" „ ^11 h;a*s ^ppjifentlf "ifigor13; EFii^bulk
pco.4 existing ,"<|ata,,"as'".'insufficient Tand ff|wed"4^ '^t m'iy t6ef6Mnd
«,. — .^3 ... .,. ~-TV. -^_..»<. (_ij - . , .. ^j >aj) - .. • , .. •. _ . jj • t p:» • £. /r; •[ OP j t'i ^j.^13^ _ j
, contusion s.._;£r
or !",proyide,d 'o'nly^ :on€ l ^tiblf cati;on
' -'
' " '' l 1(
{ " g^a.y.vli te^ca ture * :.n .
will be included in the final' critefia~d6cument" and- it":cort tains
no information counter to the proposed criteria. " ' ' •"" "k *~ fl?!'-on
of r,: t be 0 pro posed.. .-,criJ^
< ^wasyinf iuenc.ed through nqqi
....,^^. isj = _.x.^ri';/7"ind "outride M,-!of EP_A. " ^Thg, T^naJ-^prpl^ct^w3-11., °e a
-; jreeujLtrOl fe!aeseQprevi,QUs efforts, as^ "wellylg'^l'^ne'' puBiic; comment.
r--1!he finalf-griterifi will, represent, the ^gengy'slpbjectiye analysis
ii.of Ldissolv.ed oxygen, requirements o| . aquatic "prcjanlsms and the
knowledge that criteria of ten''become' standards" and unnecessarily
stringent standards can result in unnecessary socio-economic
sdhardabips. „ i... •'.-3-••:••
;;••>?.i.lH f..',:OJ 'j:-- : -
.- o 3 on \ f.: "•••:. v .•-.- i
artj e-^er'w •• no : . ..f.j -
59
-------
Comment: We -always understood and .agreed wiifeh -t
standards to pr-ovide aquatic life protection/
the proposal as the beginning of an effort
most sensitive ist'age-of the most . -sensitive aquatic
protected*-.? ^We do '-not concur '.etfdth that :apgcoa<
believe theft it; should serve as tteezifuture -baais fo,e
all receiving water standards. Rather, we vi*w
the water quality standards and stream classification process as
being one i-of designating logical-.-uses :and jreas^na-bte
criteria based on balanced maintenance of tbe^.yQY§ria;lI7~sl
ecosystem. ?That very philosophical .-'appro.ach-ohaie
cornerstone of the water quality standards.program overt.?
decade because" it allows f or., consideration^^ ^socioeeQ.moniey. as
well as biological, factors and influences. ; '-'ti^.i^ --r-s. 't:-;;or '?---j
Response: The agency has developed the criteria for disolved
oxygen '-with;-; the same : conceptual ...guides Ldeelar.edt fop ^ £ toxic
criteria, i e. that they provide for the protection of most of
the SDec~i.es "mdst of the vfefmer^and that- it, iganot:;ppssibl«r to set
limits that protect all .species-all the-time,, o.-Additionally/,-the
agency does intend that criteria do not knowingly fail to protect
valuable^Sp6cdes' a'nd thabe"protecting, a ;;pas?ticularf»spe<2ie3,fmeans
protecting^fets srmost se-asitive , (life ' stage. e^Theoageqcyswi^besnto
emphasize that socioeconomic considerations have little, if any,
roleiin' the'establishment of criteria, vrafeher socioecpn0mi<|£.ajriid
othSr-^-social -issues properly come jia.to^eplayH;'in cth¥=>~;T5p*&l
stafldards'^settingsp'r-ocess.' •. • -•'• /ri;. 70 -<^i:.-»o-/ ..cc;f i.j.x:,f c/.. .--•:-
"5. £-"tr-sD , f. j c *ar,' >,•;;-., j.c, U
Gomment-t ^ •* 1 1 >i§xdif f icult ito analyzeothe- datary.which therguidance
referenee§ - andf uses? ih developing theociciteria,3primatriiy:
the data are not consistently presented.
to the reader for data to be compiled in a table. The table
could include a summary of the various test conditions (i.e.
%emg@fa6ure *,"•'• disi^oived oxygen :; maximum.?; .minitnuHU.: Saveragsmr cand
exposure dQration? response, etci Jeoo^lsov^a sys,tfimati,cr?meTfiod'fl3f
^till'zing^ the-1 data n needs tovbe3presented-.and-_. applied.! t of -avad liable
data.
- Re sp&pse ; ^ ^ sin ^ o:f ^ ;*'. the - non standard --
available. Thus, considerable judgement must be involved in
60
-------
: dissolved oxygen criteria/ much .^of it based on
of published data (rather , vthan .the data as
-ri; £These reanalyzed data are sumraairjiz,e.d in-.^Tables 1-5
thre criteria. The ^tabular av^nid. .graphical
these reawalyses is considered tQ be a more
tabulation :rthan listing tlengthyi jatfid diverse
data. ..If.;' ^ - pru. - .
ec £j59~C"rq nor.; i n _' 3: j. o •• • £•.:••_•;;£. I ..•..;..' i^i. o ',
ift&neefeting sof staridards . and monitoring -of dissolved
m£x3yrgen-;a£n-@e'ntr#t3i?on ifcn lake>s^ar,e u not mentioned -in • sthej document.
urif or ea>«at«'ji because'/!' ewe consider the establishment of
? oxycfeu-'- ^cstandand -: f o'r . . lakes to-, :pose , problems
'different thane- those ..in lotica&environments.
Information should be provided . in fctohe t document -w.hichr e'an answer
questions such as:
e" ,03.i'f.: ^o^ t, Jr-.'i^C' • £-'.--c^- v&b . r -^t,-. . v ;• .
-theipeoposed criteria applioatible to . lakes :,in -general ,
"
2^ : 'aeerithsyqtooappiy.jonlyi to mixe<§inlayers of lakes £e pi limn ion,
me ta limn ion) JorAto the lentire water :colamn> rand'soc^q if-': 5.
;.'<=>•' t. .ic :.,.; ' : •. J ,'if. - ivon;. , .-- .:• r i •;-... j^:- .',.;<; ;-• • • ,-j ? sc-f *;
&3>rrri3Mthe^meanIcohcentratipn calculated^f or; -,the eofcai^6^ iake or
oindividual' -peiats iflwatececolumns) / -oraaeeas on. theiJak^?;i ^t-;j.
vvne r^ -i \T.^";iI e^bri ^ no u -.-<•? hie noo o ^moncoef .r occ j&rir- sr; ejSfn-
•' R6 sbpaaet - *> ' - Ttae ^a^ency ., ^assumes -that i. the, new crifeerianwiil : be
4 applied' to lakes^ just- as^ther old criteria were«. andfcf"is«awa«:.g-of
no special application problems in lakes: ; when/ the eQew,f er£,j5e,ria
replace the old. Certainly, the naturally-occuring dissolved
oxygen concentration discussion in the criteria would apply to
sfoypbldmnia: nThevmean' dissolved oxygen; concenfcgafcion i
e ttoe^^eriieriai ^is fcavsetempoBai mean/t vspafcial^&fae
- specif ie-tlceoso;dei:ations,c«; ay ee-Ac. y. -vne: t;;' j r-> -n e-::£ e; B& sno
ef-;fa r-rT ,eJds.; e._ •- j i;-sJ iqtn. i t--v o.t *t..i •30^ ^yLjHSj. .-5.^3 03
, a ,. :: ) 4- tK-t:.' ibro' •;(;*&;'-.'• 8 joj ^rt? ed., .' :; v ^ . .rrr £. ef^.lonj M^C.-D
'Comment ;-= v SS i frema'pecdf icdfay ">> may allowo for"lower-. miniraaef 9^7;
i - We: esflggest; j a siosers. reviewer pf
f orncruciaisdissolved ©jxygenevaiuesr i
address "natural flow" conditions.
£ Region se : rrsrSfictB-specificsicrdteria ayeneae resognized;
control . srU9o:.
i f brc il^eHOffecdJEistxi dissedved.. oxygen- pr i*er iavcs bSaic; «iies sspeci f ic i.ty
• o:f 'Standtafdst -isndnheren.t dn£>aisa»'attainab.i.iitgfr anaiysiS!Br;<2:oldwa,tsr
^•n& warmwauterc'cdesignia'tlom^^ ia^Ee stage7dlit»3t05iyY;rand econppic
-•* «>h's4 derations. :s';v>.ThebPvora.£eariai -' ref>re!senfc;r>sgii4d*lines for
•3«.s>feabli'shmeref.ioXD astandaards . €£>ri-->*:he^proi€C,tifliai h of 3 aqua tic life.
vfljfien is difficult to provide a
:- sg^ffieraidzedr -iasdsi for .ief f l.uentt ,. dominated streams beyond the
: j^jn-
61
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discussion of natural dissolved oxygen concentrations already
provided in the document. 'PY ?•- s
r '-
Comment; As pointed out in the criteria docUfieflt?*''- niu£n more
information exists on the single family Salmonidafe -and its sev&h
genera than on any other family or group. Queittons° _^The- age&cy belije^vfiSr^.thai': ,su"f f ic^ieji^t" 'Vyide,n.ce
existiS-: tor show : thatnv- .labpra^pryf-expa^d" $rg&n.iLsri(s^B rVspori^.^pce
oibgandi«smsysimi3.arly:> .exposed; in ther,£f i^fld.,- _._« J^bir,a±o'ryf,,_d^^
appeatf-: toibe ^.-the r;pripar-y togxl of. c^ite-r.ia^ ...dey^^nieiit fax^. "s|>m>
time to come/ although ^^eg^^io^e-ofs^J[ii^^^_.'
desirable goal.
••>3 Y^Pv|£ -.-Lvocji. .'J'-i-r. --;D &K-t:.r e:.U v J v 5 w tr :?
rl:; iriv- £.e'7?i pr i-y>^qe ;./ir c -tc j. r- £•. .;c :-c vsne
'
oxygien t, .pirob\l®jnf) ;w iitL^ rtaice ai ^iacd / r ocitt i c a 1,. jlopk-. a t. rrt he a,dy,a rv tjacj ejs
«6«pl«iyg.ngs partial pxw«aami« lijn&rfesrerath^r .- ..jihja^h
«ait«r» 5otln e.:mjb o.piniMC»rte*npt3he his.tQ-r^.ca'J.j 5
^1 i mits a ner .unrJaaclL'iqB t i.c- <& heirp t ejope r s;tyi r e 0 j»n;q|> re
taken" Into aaccofuntr. pni^t'b ro. ^f.^ j ^,o epc-:? £.':;.!' v,'- -. r.~ oniv'.
••• ••--•' ^t-s^ ^r-oJ-ax: s.^-. , -, ;^ neupebf-c" . y iOrnoi rt, s,vp si
Response^ L?T Tbei'ag?enEyol rtevJi-fiW.eJd.rcthec.6^pPSri,triionsi-j9f those .vfa;
each of the three methods for expressing diss.Orljyeol: rQX'
partial pressure, and percent saturation). In each case there
were advantages j^ahs*c-idisjadivarntfeag.e-s vofaa • ;wftli ^ as o-%heoce- "=e^f&e-.ct rro.fe •- ;altictude -rrOn ssp.];v:-ed
oxygen requirements; 3) relatix>n;steip^-tTetween;5tlae measure .a 0
-------
--- "IE
Y^'BS'llSgnO.il'Sti:?";?"" ,:.
amount of oxygen delivered to the cells; and 4) ease of use of'
the measure. ''c-
soon, ^Smd^iSijflR to use m<3/L was based on the considerations^
t^isgrCmpre .-straight-forward and familiar than percent
orngar|:ial "pressure; 2) a number of emminent fis-lr-
s' rg" with no advantage for either measure;" and
7y '^s "'•Jie'imMt^ur^^tops the requirement for dissolved^oxygen
dropsV" ''"tJu%:' while 'mg/L would remain the same/ both percent
saturation and partial pressure would mandate an increase ^in the
dissolved. oxygen concentration.
rsr-;: B^~ rr oor?s?i {o.ueg6 • fio
iT-.-ac-^: 'j.or. anc. .':.:•' b ,101, f .."*• . '" '
^Cbnfmtenxg ffii rgsireV'Raised by EPA aiej
«fi-*5 11 %'^t".,. ., £'; . .. 1; .-»i; . -.^ T J • «f ^ »r i'
/ ;,r,..'^ "TftTpitrs F'e^T&r^ti;i^6gister Announcement of the
^^e^^ms%^v!e%::976%yg^n•;t cr-l^ferl'a9 ; f cfr -'public^cam
^Va ?'-ay»-^1?®aa^/trv^a-'^l' "' +TI''& o r-iifffT <-
invite^ specif ic corament oar these
HovP'2-srhoul'd .
hb%Pcs1iO'U Id- ^t
be-
In general/ the early life stage criteria should apply to
significant fishery populations and spawning areas which need to
' '
s>'e53-ies=/~- -"s^ftJh . ra'a^rths Saatheaiil «jninaia>w;jowe^JivDanc be->ofi a
siIs''.^--rb p.iie£t,^qj-.& ^c-3 aboH^sni s^^rl.i eri ""?3" i
r.I. . ( nc - ieiij^te. 3nfc:isq fcns .. sifee £•- -; ••
guiidance.if or cdewsafLnapaEngs j«a s tferle a dssal locations for
cdeinrand> JauggaafeaiJth^ute jtdieijTQ.lO for the warmest
Sfti!0''n1feh; 3?e^vise(id-/ "wiftfih'-- mc?del=ed'? sfeermpe-tatnir es?, -equal to the average
CKfat - 'raxSrtteh. ; ?. Olkisis-^aeems; ;- treasonable and could be
'f or soLda'lfcu^laCing a jwai^feelQad --allocations to protect
liifeei ^s'tage^s.-'J^'Eiheaeieaire, .-most often cooler months/ with
higher low flow values."
** * — \ ' '
63 .
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res»toiPU ? c\ +
1 Resistance to Puccinia coronata svenae in induced mutants of
Avense sativa. Behizadeh* Susan N32ele» 1979
?2 Response to public comments on the preliminary water Quality
ni3n32enient plan* >i\linois Environmental Protection Agency The
Asfenc«» 1979
3 Re^pons^s to public comments on the proposed general Guidelines
for recommendation of sites for nuclear waste repositories J draft* Ma
27,4983, DOE» 1983
24 JLF: NMS
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dis?ox»crj\+
BIS»OX»CR> is not in TITLE index.
DIS»OX»CR»R is not in TITLE index.
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